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Evolution of marine ecosystems, a global view from the Early Cretaceous marine tetrapods of Colombia

  • Redpath Museum - McGill University
Vertebrate Anatomy Morphology Palaeontology
ISSN 2292-1389
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Published 21 May, 2021
Editors: Alison M. Murray, Hallie Street and Robert B. Holmes
© 2021 by the authors
DOI 10.18435/vamp29374
Meeting Logo Design: Our 2021 meeting logo (front cover) is by Matthew Rhodes. He says the design is “a tribute to the ‘academ-
ic ancestor’ of Canadian vertebrate palaeontology, Robert “Bob” Lynn Carroll (1938–2020). Carroll represents Canadian palaeontology
not only by his own contributions to the eld, but also by the ‘academic radiation’ of his numerous students, many of whom continue
to shape the eld today. Much of Carroll’s research was dedicated to early tetrapods, particularly from eastern Canada. is led me to
his 1969 description of Paleothyris, an early reptile oen used as a representative of the anapsid skull condition, including in his own
book Vertebrate Paleontology and Evolution. e Paleothyris climbing through the logo was inspired by Figure 12 of Carroll (1969),
which cuts o around the base of the tail—the same position at which the logo turns into digital blocks. Carrolls works oen have
Romerograms (spindle diagrams), so a maple leaf-shaped one materializing from the V seemed appropriate. On a deeper level, the
Paleothyris sits at the base of the V as if it was the ancestor of the Romerograms central branch, echoing one of Carroll’s lines quoted in
Caldwell and Larsson (2020) in VAMP: “... if you believe in evolution, you have to believe in ancestors, and I’m going to keep looking
for them until I drop. ”
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
9th Annual Meeting
Canadian Society of
Vertebrate Palaeontology
May 26–28, 2021
Vertebrate Anatomy Morphology Palaeontology 9:139
Message from the Organizing Committee
Greetings to our members across Canada and around the world
What kind of year has it been? Travel restrictions and work-from-home orders have limited our abilities to
meet, use lab facilities, and conduct eldwork. Regardless, vertebrate palaeontology research has adapted
and progressed, though maybe in dierent directions than were anticipated at the beginning of 2020. is
year’s annual meeting nds us at a sensitive crossroads during the Covid-19 pandemic, balanced between the
increasing availability of vaccines and the concerns over the spread of new variants. Staying connected and
inspired may be particularly important during these uncertain times, and so the Society felt it was important
to have an annual meeting this year. erefore we are venturing into the realm of digital conferencing.
e CSVP 2021 meeting will be held on May 2628th with an introductory guest lecture by Dr. Grant Zazula
on May 25th. e oral presentations will be given live using Zoom (a video conference soware), and digital
posters will be available throughout the meeting with a live session for questions and discussions. e Virtual
Organizing Committee and the Executive Committee are aware of just how much of our interactions take
place via similar media these days, and so the decision was made to limit the conference to a few hours each
aernoon/evening. We hope this makes the annual meeting accessible to all our members without being
overwhelming. e reduced time did limit the number of presentations we were able to accept, and so we
hope that members of the Society understand our choice to prioritize students and early career researchers.
ere are, of course, aspects of an in-person conference that we cannot replicate virtually. However, without
the need to pay for travel or accommodations, the virtual format of CSVP 2021 has attracted interest from
students and researchers across Canada and from as far aeld as Europe and Asia. We are grateful for the
dedication, patience, and exibility the members of our community have shown to each other and to the
Society over the past een months. We hope members can make the best of the virtual meeting this year,
and we look forward to our next opportunity to meet in person,
Your Virtual Organizing Committee,
Bassel Arnaout
Emily Bamforth
Julien Divay
Annie McIntosh
Hallie Street
Yan-Yin Wang
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
Message from the Host Committee
Lissamphibia: a polyphyletic group within Temnospondyli?
omas Arbez ........8
First occurrence of a sea turtle (clade Panchelonioidea, superfamily Chelonioidea) from the Dinosaur Park
Formation of Saskatchewan, Canada
Emily L. Bamforth and Hallie P. Street ........9
Potential preservation of keratinous tissues associated with frill ornamentation of an immature Centrosaurus
(Ornithischia, Ceratopsidae)
Caleb Brown ........10
Development and evolution of regionalization within the avian axial column
Hoai-Nam N. Bui and Hans C.E. Larsson ........11
First denitive occurrence of Polycotylidae (short-necked plesiosaurians) from non-marine sediments of the
Dinosaur Park Formation of Alberta: evidence for a multi-taxic, freshwater plesiosaurian assemblage
James A. Campbell and Caleb M. Brown ........12
PalaeoPoems: A digital anthology highlighting a unique form of science communication
Brigid E. Christison, Michael G.W. ompson, and Katrin Emery ........13
Evolution of marine ecosystems, a global view from the Early Cretaceous marine tetrapods of Colombia
Dirley Cortés, Hans C.E. Larsson, Erin E. Maxwell, Alexandre Demers-Potvin, Hoai-Nam Bui, Anthony Smith, and
Mary Luz Parra-Ruge ........14
Morphological analysis of a nectridean lepospondyl, Diceratosaurus, from Linton and Five Points, Ohio
Jamey H.M. Creighton and Jason S. Anderson ........15
A morphometric analysis of the turtle manus and its implications for the palaeoecology of extinct turtles
omas W. Dudgeon, Marissa C.H. Livius, and Jordan C. Mallon ........16
A new plastomenine trionychid (Testudines: pan-Trionychidae) from the Milk River Formation of Southern
Alberta (Cretaceous: Santonian)
Shauna C. Edgar, Don B. Brinkman, Michael J. Ryan, and David C. Evans ........17
Life history of an archaic placental mammal, Pantolambda bathmodon (Placentalia, Pantodonta)
Gregory F. Funston, Paige E. dePolo, Sarah L. Shelley, John R. Wible, omas E. Williamson, and Stephen L. Brusatte
Revisiting the sedimentology and depositional evolution of the Cypress Hills Formation (Eocene – Miocene)
in southwestern Saskatchewan, Canada: implications for vertebrate microfossil assemblages
Meagan M. Gilbert ........18
Dinosaur fossil discovery using remotely piloted aircra systems and spectral mixture analysis
Sean Herridge-Berry, Caleb M. Brown, Derek R. Peddle, Brian J. Pickles, and Craig A. Coburn ........19
Feeding ecology of the Bearpaw Formation mosasaur community
Femke M. Holwerda ........21
Vertebrate Anatomy Morphology Palaeontology 9:139
Osteohistology of a thescelosaurid (Dinosauria, Ornithischia) bula from the Wapiti Formation (Campanian)
of Northern Alberta: implications for diversity of growth strategies and osteohistological features within
Michael Naylor Hudgins, Phil R. Bell, Nicolás E. Campione, Federico Fanti, Robin L. Sissons, Matthew J. Vavrek,
Derek W. Larson, and Corwin Sullivan ........22
Impacts of Miocene tectonism and climate change on diversity dynamics of carnivoran and ungulate
mammals in North America
Blue Hunter-Moatt, and Danielle Fraser ........23
New material of the oldest metamorphic salamander (Amphibia, Urodela) from the Middle Jurassic of China
yields insights into palaeoecological disparity
Jia Jia, Jason S. Anderson, and Ke-Qin Gao ........24
Vertebrate diversity trends and chrono-, litho-, chemo-, and cyclostratigraphy of the Late Cretaceous
Manitoba Escarpment in Saskatchewan and Manitoba, Canada
Aaron A. Kilmury, Michelle P.B. Nicolas, and Kirstin S. Brink ........25
e internal cranial anatomy of Panoplosaurus mirus (Dinosauria: Nodosauridae)
Marissa C.H. Livius, Hillary C. Maddin, Michael J. Ryan, Jordan C. Mallon ........26
First record of a parasaurolophin hadrosaur from the Oldman Formation of southern Alberta
Bradley D. McFeeters, David C. Evans, Michael J. Ryan, and Hillary C. Maddin ........26
Palaeobiodiversity statistics and paleoenvironmental implications of microvertebrate localities from the
Frenchman Formation (Latest Cretaceous, Maastrichtian) of Saskatchewan, Canada
Jack R. Milligan, and Emily L. Bamforth ........27
A bird coracoid from the Horseshoe Canyon Formation (earliest Maastrichtian) of Alberta, Canada
Sydney R. Mohr, Gregory F. Funston, and omas A. Stidham ........28
A quantitative analysis of morphological variation in dentition among escelosauridae with implications for
thescelosaurid palaeoecology, macroevolution, and microsite identication
Nathaniel E.D. Morley, Michael Naylor Hudgins, Caleb M. Brown, Philip J. Currie, Han Feng-Lu, and Corwin Sullivan
New data on the distal tarsals of Ornithomimidae provided by a partially articulated specimen from the
Kaiparowits Formation (late Campanian) of southern Utah, USA
Rachel E. Nottrodt and Andrew A. Farke ........30
New shallow snouted species of Velociraptor sheds light on intraspecic variation in Velociraptor mongoliensis
and possible niche partitioning between species
Mark J. Powers, Mark A. Norell, and Philip J. Currie ........31
Reconstructing life history of the sabre-toothed cat Smilodon fatalis using bone histology
Ashley R. Reynolds ........32
Identifying competitive exclusion in the vertebrate fossil record: lessons from early vertebrate morphometrics
Bradley Scott and Philip Anderson ........33
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
A hesperornithiform (Avialae: Ornithuromorpha) from the Upper Cretaceous Nemegt Formation (lower
Maastrichtian) in Mongolia
Tomonori Tanaka, Yoshitsugu Kobayashi, Yuong-Nam Lee, Robin Sissons, Michael Ryan, Tsogtbaatar Chinzorig, and
Khishigjav Tsogtbaatar ........35
A kinetic model of the palaeognath ribcage with implications for understanding avian ventilation
Yan-yin Wang, and Corwin Sullivan ........36
Taxonomy of a new goniopholidid specimen from the Upper Jurassic Morrison Formation and their diversity
in North America
Junki Yoshida, Atsushi Hori, Yoshitsugu Kobayashi, Michael J. Ryan, Yuji Takakuwa, and Yoshikazu Hasegawa ........37
How to make monsters: cladistic analysis of ontogeny recovered evidence of anagenesis in North American
Amelia R. Zietlow ........38
Vertebrate Anatomy Morphology Palaeontology 9:139
Lissamphibia: a polyphyletic group within Temnospondyli?
omas Arbez
Department of Earth Sciences, Carleton University, Ottawa, ON, Canada;
Phylogenetic relationships between lissamphibians (frogs, salamanders and caecilians) and their fossil relatives
(i.e., non-amniotic extinct tetrapods) is a century old question, yet still actively debated, and in spite of phylo-
genetic matrices including more and more taxa and characters.
Several hypotheses about Lissamphibia relationships are still discussed: Lissamphibia as a monophyletic
group included among the Temnospondyli (Temnospondyl Hypothesis – “TH”), or among lepospondyls
(Lepospondyl Hypothesis - “LH”), or as a polyphyletic group divided among the temnospondyls and lepo-
spondyls (Polyphyletic Hypothesis – “PH”).
e absence of consensus regarding the position of lissamphibians is attributed to the lack of specimens
displaying a mosaic of characters specic to lissamphibians and to a particular clade of extinct non-amniote
tetrapods. e most ancient fossils attributed to lissamphibians are indeed already extremely similar to extant
lissamphibians and share few similarities with extinct non-amniote tetrapods. is dierence is particularly vis-
ible with the great reduction of the number of cranial bones in the extant lissamphibians by comparison with the
extinct non-amniote tetrapods.
Here, a cladistic phylogenetic analysis made with PAUP and including all the major groups of extinct non-am-
niote tetrapods, as well as lissamphibians and amniotes (63 taxa and 213 characters), reveals methodological as-
pects also have an important inuence on the resolution of lissamphibian relationships. e phylogenetic analysis
was divided into three variants (when compared to a reference) in order to test dierent character treatments
(e.g., ordered vs unordered characters), as well as the impact of the inclusion or exclusion of some characters
(e.g., character coding the presence or absence of a given bone).
Interestingly, dierent hypotheses of the position of lissamphibians, as well as their monophyly or polyphyly,
were recovered based on dierent tests of the same matrix, allowing comparison of these hypotheses within a
constrained framework (i.e., comparing topologies that are not the product of analyses with great dierences in
taxon or character sampling, as it could be when comparing dierent studies).
e comparison of the dierent hypotheses recovered here, in terms of tree length, character support as well as
character transformation coherence shows that the lissamphibian’s monophyly (TH and LH) is mainly supported
by the “absence of bones” without any exclusive synapomorphies.
A hypothesis of a polyphyletic Lissamphibia within Temnospondyli (TH-p), where frog and salamanders are
found within the Dissorophoidea and caecilians are found within Brachyopidae, appears to be the most coherent
in terms of character transformations despite not being the most parsimonious overall (by a few steps). In addi-
tion, the TH-p hypothesis seems to solve several inconsistencies among the TH, LH and PH (e.g., multiple bone
reappearances or multiple reversions of morphologically complex character states).
So, the classical view of a monophyletic Lissamphibia is weakly anatomically supported as the synapomorphies
would only be the “absence of bones”. e resulting similarity appears to be due to a similar cranial simplica-
tion process already known to be happen convergently in dierent extinct non amniotic tetrapod groups (e.g.,
Lepospondyls) and likely due to paedomorphosis events. e fact that frogs, salamanders and caecilians do not
form a monophyletic group when including extinct non-amniote tetrapods would explain why currently all the
synapomorphies exclusive to the Lissamphibia are based on soft tissues and not hard tissues, such as bones.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
First occurrence of a sea turtle (clade Panchelonioidea,
superfamily Chelonioidea) from the Dinosaur Park
Formation of Saskatchewan, Canada
Emily L. Bamforth1,2 and Hallie P. Street3
1Royal Saskatchewan Museum, T. rex Discovery Centre, Eastend, SK, S0N 0T0, Canada;
2University of Saskatchewan, Department of Geological Sciences. Saskatoon, SK, S7N 5E2, Canada
3Edmonton, AB, Canada;
ough relatively uncommon, sea turtles (clade Panchelonioidea) are an intriguing component of western
Canada’s Cretaceous marine faunas. Studies of panchelonioid diversity patterns within the Late Cretaceous
Western Interior Sea suggest, for reasons not yet fully understood, that these animals favoured southern portions
of the Western Interior Sea (Nicholls and Russell 1990), occurring much less frequently in Canada than in the
United States. In Saskatchewan, panchelonioids are represented by just two occurrences from the Santonian
Niobrara Formation along the Manitoba Escarpment, and one from the upper Campanian Bearpaw Formation
of southwest Saskatchewan (Nicholls et al. 1990). e Niobrara Formation specimens, a humerus (RSKM
P2077.64) and other fragmentary remains (RSKM P2077.31) were described by Nicholls et al. (1990) as proto-
stegids, largely based on their small size. Protostegidae is an extinct basal panchelonioid group which includes
the giant sea turtle Archelon. It is the sister taxon to the Chelonioidea, which includes nearly all other known sea
turtles (Evers et al., 2019). e Bearpaw Formation specimens, small rib pieces and a badly weathered peripheral
fragment (CMN 40660), could not be identied beyond Chelonioidea (Nicholls et al. 1990).
Herein is described the rst occurrence of a chelonioid sea turtle from marine strata within the Dinosaur Park
Formation of Saskatchewan. RSKM P3197.198 is a left costal plate of the carapace, with a maximal length of
150 mm, maximal width of 90 mm in width, and maximal thickness of 16 mm. While broken along its medial
margin, the lateral peripheral edge is reasonably well preserved. e costal plate is broad and slightly convex dor-
sally, with no noticeable suturing or ornamentation. e specimen was collected in 2016 from a marine bonebed
near the hamlet of Herschel, Saskatchewan. Recent studies have placed the Herschel Marine Bonebed (HMB)
within a marine interval of the upper Dinosaur Park Formation, in a shallow-marine barrier-island basin environ-
ment (Street et al. 2019). e HMB has yielded a high diversity of marine vertebrates, including ichthyodectids,
Enchodus sp., Protosphyraena sp., Ischyodus rayhaasi, hybodontids, odontaspidids and other lamniforms, as well as
polycotylid and elasmosaurid plesiosaurs, and mosasaurine and plioplatecarpine mosasaurs.
In a review of marine turtles from the Late Cretaceous of Alberta, Brinkman et al. (2015) identied at least
three genera of chelonioids from this province: Nichollsemys, Lophochelys and Kimurachelys. Nichollsemys is
known from open marine sediments of the Bearpaw Formation (Brinkman et al. 2006), while Kimurachelys
and the specimens ascribed to Lophochelys are from the Lethbridge Coal Zone of the uppermost Dinosaur Park
Formation (Brinkman et al. 2015). RSM P3197.198 is signicantly larger than the Alberta specimens referred to
Lophochelys, and both Nichollsemys and Kimurachelys are known only from cranial material. erefore, more work
and more specimens will be required to determine if RSKM P3197.198 can be ascribed to any of these taxa, or if
it represents the rst occurrence of another taxon in the northern Western Interior Seaway.
Comparison of RSKM P3197.198 from the HMB with the Alberta material raises an intriguing question
about the possible paleoenvironmental preference of Canadian chelonioids. Although not necessarily directly
contemporaneous with the Lethbridge Coal Zone, the HMB represents a similar shallow-marine, nearshore
environment. Brinkman et al. (2015) suggested that chelonioids may have been brackish-water or even freshwater
tolerant. is may also apply to RSKM P3197.198, which was found in a similar paleoenviroment. Although
the sample size is small, chelonioid diversity appears to be higher in nearshore, shallow-marine or estuarine
Vertebrate Anatomy Morphology Palaeontology 9:139
deposits. More specimens and more research could help to elucidate is this was a true biological signature, and if
chelonioid sea turtles preferred these habitats over the open ocean.
RSM P3197.198 represents the largest and most diagnostic chelonioid specimen known from Saskatchewan.
e collection of additional specimens from marine sediments of the Dinosaur Park Formation may reveal im-
portant information on the diversity and paleoecology of marine turtles in western Canada.
Literature Cited
Brinkman, D., M. Hart, H. Jamniczky, and M. Colbert. 2006. Nichollsemys baieri gen. et sp. nov, a primitive chelonioid
turtle from the late Campanian of North America. Paludicola 5:111124.
Brinkman, D.B., M. Densmore, M. Rabi, M.J. Ryan and D.C. Evans. 2015. Marine turtles from the Late Cretaceous of
Alberta, Canada. Canadian Journal of Earth Sciences 52:581589.
Evers, S.W., P.M. Barrett., and R.B.J. Benson. 2019. Anatomy of Rhinochelys pulchriceps (Protostegidae) and marine
adaptation during the early evolution of chelonioids. PeerJ 7:6811.
Nicholls, E.L., and A.P. Russell. 1990. Paleobiogeography of the Cretaceous Western Interior Seaway of North America:
the vertebrate evidence. Palaeogeography, Palaeoclimatology, Palaeoecology 79:149–169.
Nicholls, E.L., T.T. Tokaryk, and L.V. Hills. 1990. Cretaceous marine turtles from the Western Interior Seaway of
Canada. Canadian Journal of Earth Sciences 27:1288–1298.
Street, H.P., E.L. Bamforth, and M.M. Gilbert. 2019. e formation of a marine bonebed at the Upper Cretaceous
Dinosaur Park-Bearpaw transition of west-central Saskatchewan, Canada. Frontiers in Earth Science 7:209.
Potential preservation of keratinous tissues associated
with frill ornamentation of an immature Centrosaurus
(Ornithischia, Ceratopsidae)
Caleb Brown
Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, AB, Canada, T0J 0Y0;
e recognition and description of keratinized epidermal structures in dinosaurs is becoming increasing-
ly common. Within Ornithischia these keratinous structures include bristles/laments (Psittacosauridae,
Heterodontosauridae, Neornithischia), scaly skin (various taxa), keratinous osteoderm scales (Ankylosauria),
rhamphothecae (i.e., keratinized beaks) (Hadrosauridae), and hooves (Hadrosauridae/Ankylosauria). e skulls
of the Ceratopsidae possess several bony (i.e., osseous) features which were likely capped by robust keratinized
tissues including rhamphothecae on the rostral (i.e., rhinotheca) and predentary (i.e., gnathotheca), and keratin-
ous sheaths for the nasal and postorbital horns, and likely the frill and jugal horns (i.e., epiossications) as well.
Despite this high potential for keratinous preservation in ceratopsid skulls, and the abundant fossil record of this
group, direct evidence of its preservation is rare to non-existent.
In 2019, a small parietal of Centrosaurus (TMP 2019.012.0122) was collected from low in the Dinosaur Park
Formation (Campanian) of Alberta. During preparation, the preparator discovered several at, semi-circular to
crescentic structures located under (i.e., stratigraphically beneath) the parietal within the jacket. Importantly, a
broken and displaced section of lateral ramus of the parietal was found at the same level as these structures. Due to
their shape and association they were initially thought to be unfused frill epiossications (i.e., epiparietals), however
breaks reveal their composition to be entirely ironstone with no bone component. A return to the quarry later in the
season located more structures in the spoil pile of the jacket (i.e., matrix removed to lighten the jacket).
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
In total eight structures are preserved. e specimens vary from semi-circular to crescentic in shape, with the
curved/convex margins having a rounded beveled edge, while the at/concave ‘basal’ margin often shows a con-
cave facet-like edge. e basal margin of one specimen also shows a bi-lobed facet reminiscent of the epiossica-
tion spanning the parietal squamosal contact. e specimens vary in size, with basal widths of 30-80 mm, basal-
apical heights of 21–41 mm, and thickness of 6–11 mm, with these three measurements scaling approximately
isometrically. e surface texture of the structures is distinctive, bearing parallel ridges and grooves, approximate-
ly 1 mm in width. In particular, on the rounded margins these striae form a distinctive braided or ropey appear-
ance with parallel lineation showing a larger-scale sigmoidal pattern along the periphery of the elements. More
centrally, one of the at surfaces of each element shows a radial pattern of striae, while the opposite side has a
subtler and more random pattern.
e parietal preserves the midline bar, right lateral ramus and much of the posterior ramus, missing the left
side. P1 loci (the medial-most parietal horn positions) are preserved on both left and right sides of the parietal,
with a gap in the right P2 (and P3?) area, followed by four right lateral loci (P3–P6 or P4–P7 — lateral pari-
etal horn positions) to the squamosal suture, with all loci expressed as thin, subtle scallops. e parietal is 391
mm long (sagittal length) and 317 mm wide (right half width), one of the smallest known for Centrosaurus. e
thickness and convex rounded bevel of the posterior and lateral edge of the parietal correlate well with both the
thickness and concave facets on the at edge of the structures.
e size, shape, ornamentation development, and mottled texture of the parietal are consistent with an early sub-
adult stage, comparable to, but smaller and potential earlier than, TMP 1995.175.0064 (470 mm x 335 mm) and
CMN 11839 (496 mm x 366 mm). Centrosaurine parietals of similar, or younger, ontogenetic stage are not known
to have preserved epiossications, whereas larger/older specimens show associated and then fused epiossications.
ese structures are tentatively identied as fossils preserving the shape, but not organics, of keratinous sheaths
associated with parietal horn loci. If this interpretation is correct, this specimen indicates that that keratinous
horns may ontogenetically precede the development of the epiossication at parietal loci. Further, the size of
these keratinous horns is larger and more exaggerated than would be expected for a specimen at this ontogenetic
stage. Alternate interpretations or identications of these structures are welcome.
Development and evolution of regionalization within
the avian axial column
Hoai-Nam N. Bui and Hans C.E. Larsson
Redpath Museum, McGill University, Montreal, QC, H3A 2K6, Canada;;
e origin of birds from their terrestrial antecedents was accompanied by a wholesale transformation of their
skeleton as they transitioned from a terrestrial to an aerial realm. A signicant aspect of this dramatic transform-
ation is the reduction of separate vertebral elements into regional fusions to increase axial rigidity. Specically,
the transition from non-avialian theropods to highly derived birds is accompanied with the loss of an elongate
tail, fusion of posterior caudals into a pygostyle, a broadly fused synsacrum and, sometimes, a notarium. is is
partially mirrored within the development of the axial column, with the axial column experiencing increasing
regionalization and the loss of individual skeletal elements through vertebral fusions. Using a detailed description
of the morphological development of the axial column in the model domestic chicken, Gallus gallus, we present
a map of axial chondrication and ossication based on discrete characters. We nd that delays in ossication
occur in conjunction with the formation of fusions. Our study shows that the pattern and sequence of fusion and
ossication during development may reect the presence of independent modules, or functional units, as subsets
Vertebrate Anatomy Morphology Palaeontology 9:139
within the typical regions of the avian axial column. Interestingly, few of these fusion modules correspond to the
initial axial Hox expression patterns, suggesting another patterning mechanism is driving axial fusion regional-
ization. Additionally, two regions of fusion are discovered in the synsacrum. e anterior region of seven fused
synsacrals may correspond to the non-ornithuran pygostylian synsacrum of the same number of vertebrae. is
work provides further insight into the evolution of modern birds utilizing an integration of anatomical, develop-
mental and evolutionary perspectives that can be used for future applications in paleontology.
First denitive occurrence of Polycotylidae (short-
necked plesiosaurians) from non-marine sediments of
the Dinosaur Park Formation of Alberta: evidence for
a multi-taxic, freshwater plesiosaurian assemblage
James A. Campbell1 and Caleb M. Brown2
1Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada;
2Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, AB, T0J 0Y0, Canada;
Non-marine to paralic sediments of the Dinosaur Park Formation (DPF) have produced a stratigraphically ex-
tensive record of plesiosaurian remains (n = 105 individuals). e majority of this material comes from Dinosaur
Provincial Park (DPP), where the DPF is approximately 70 m thick. About 42% of this material is diagnostic to
the family level, of which the majority (95%) is referable to Elasmosauridae (i.e., long-necked plesiosaurians).
About 19% of the elasmosaurid material is referable to the recently named Fluvionectes sloanae, whose remains
extend from 25 to 56 m above the base of the DPF. In addition to these elasmosaurid occurrences, three isolated
teeth (TMP 1987.048.0042, 2001.012.0151, and 2002.012.0051) from the DPF of DPP were tentatively iden-
tied as polycotylid (i.e., short-necked plesiosaurians) in 2005. ese teeth represent the only published evidence
that polycotylids inhabited non-marine to paralic environments of the DPF. Juvenile polycotylid remains are also
known from marginal marine sediments of the DPF near Herschel, Saskatchewan.
We re-examined these teeth and found that they are labiolingually compressed and have smooth (i.e., lacking
enamel ridges) labial surfaces, as in elasmosaurids but not polycotylids, and are morphologically similar to those
of Fluvionectes; we therefore identify them as elasmosaurid. Although this would bring the occurrence of poly-
cotylids from the DPF of Alberta into doubt, we also report on two previously undescribed isolated polycotyl-
id centra (TMP 1980.016.0422 and 2020.012.0008) from the DPF in DPP. Both specimens are identied as
cervical centra, based on the presence of rib facets, and a ventral keel separating two foramina subcentralia. e
neural arch appears to be unfused in both specimens, suggesting that these individuals had not reached full osteo-
logical maturity, as is the case for most plesiosaurian remains from the DPF. ese centra are nearly circular in
articular view and are anteroposteriorly short, both of which are characteristic of polycotylids. ese centra would
have been slightly longer in life, as the articular rims have been lost to abrasion. Taking this into account, these
centra are proportionately shorter than most other polycotylid taxa, so this may represent a diagnostic feature.
Both specimens were collected from an interval between 30 and 40 m above the base of the DPF, overlapping
with Fluvionectes, from palaeochannel sediments that are thought to have been deposited at least 100 km inland
from the Western Interior Seaway. It is likely that these centra were transported a considerable distance down-
river, given their isolated and moderately abraded conditions.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
We believe that the low ratio of polycotylids relative to elasmosaurids (1:21) in non-marine to paralic sedi-
ments of the DPF likely represents an ecological signal and not a sampling or taphonomic bias, given the
long history of plesiosaurians collected from this unit, and the two clades having similar taphonomic proles.
Elasmosaurid remains are also more abundant than polycotylid remains in marginal marine sediments of the
DPF near Herschel, Saskatchewan, and in the marine Bearpaw Formation. Plesiosaurian remains are particularly
common in the interval of the DPF that produced these two centra, which may in part explain why polycotyl-
ids have not yet been found elsewhere in this unit. e DPF represents one of only ve multi-taxic, non-marine
plesiosaurian assemblages known, the others being the Late Jurassic Spilsby Sandstone Formation of England,
the Berriasian Deister Formation of Germany, and the late Campanian/early Maastrichtian La Colonia and
Allen formations of Argentina. e diering diet and feeding strategies between polycotylids and elasmosaurids,
as reected in their tooth and cranial morphologies, may have enabled these two families to co-exist within the
non-marine to paralic DPF, as they did in the marine realm.
PalaeoPoems: A digital anthology highlighting a
unique form of science communication
Brigid E. Christison1, Michael G.W. ompson2, and Katrin Emery3
1Biology Department, Carleton University, 1125 Colonel By Drive, Ottawa ON, K1S 5B6, Canada; brigidchristison.
2Museum of Natural Sciences, University of Saskatchewan, 114 Science Place, Saskatoon SK, S7N 5E2, Canada;
3Ottawa, ON, K1Y 2V4, Canada;
Poetry is a form of science communication (SciComm) that is able to express the thoughts and feelings of those
who study fossils in a unique way. Poetry can communicate scientic concepts in a language that is accessible to a
wider audience than academic writing alone. is a digital anthology founded in 2018 that aims
to compile as many of these poems as possible. Academics have written poetry to discuss complex scientic ideas,
feuds, and even morphological descriptions since at least the 1800s and continue to do so. ese poems are there-
fore both educational and historically signicant, letting readers understand prevailing ideas about palaeontology
from the times they were written. aims to make these poems as available as possible to both researchers and the public by pre-
senting them alongside their primary sources. Each month, features a poem related to the eld of
palaeontology, accompanied by analyses of the historical and scientic aspects of their written content. ese break-
downs allow readers to understand the terminology used within and provide context for certain verses. Featured
poems are also accompanied by contemporary artwork from dierent artists. By including contemporary artwork
with each poem, our goal is to show that historical poetry is not merely an outdated curiosity, but still retains value
as a genuine form of modern SciComm. Contemporary artwork highlights the scientic message of the poems
themselves in ways that are also promotional for each featured poem, allowing the blog to reach a wider audience.
Another major goal of the PalaeoPoems project is to encourage poetry writing among academics and palaeontol-
ogy enthusiasts. issues weekly poetry-writing prompts on social media, usually about a relatively
broad palaeontological topic. For scientists not used to writing in verse, these poem prompts are an opportunity
to think about topics in a less conventional way. Our goal with this challenge is to promote the practice of writing
PalaeoPoems so that academics, science communicators, and other people can become more familiar with these ways
of writing and thinking and in turn inform them about the value of poetry and other writing styles as SciComm.
Vertebrate Anatomy Morphology Palaeontology 9:139
Evolution of marine ecosystems, a global view from
the Early Cretaceous marine tetrapods of Colombia
Dirley Cortés1,2,3, Hans C.E. Larsson1, Erin E. Maxwell4, Alexandre
Demers-Potvin1, Hoai-Nam Bui1, Anthony Smith1, and Mary Luz Parra-Ruge3
1Redpath Museum, Biology Department, McGill University, 859 Sherbrooke St. W., Montréal QC H3A 0C4, Canada;;;; hoai-nam.bui@mail.;
2Smithsonian Tropical Research Institute, Balboa-Ancón 0843–03092, Panamá, Panamá
3Centro de Investigaciones Paleontológicas, Kilómetro 5.2 vía Santa Sofía, Villa de Leyva, Colombia;
4Staatliches Museum für Naturkunde, Rosenstein 1, 70191 Stuttgart, Germany;
is research investigates how the ancient marine ecosystems spanning the establishment of the Hispanic
Corridor (a seaway linking the eastern Pacic and western Tethyan oceans) evolved, and assembles a comprehen-
sive dataset from multiple diverse fossil localities that temporally and spatially span a time of large-scale global sea
level rise, temperature rise, and tectonic rifting that connected the Atlantic and Pacic Oceans during the Early
Cretaceous, over 130 million years ago. ese data will be used to estimate the aspects of these ecosystems that
were most stable and which evolved during this dramatic environmental event. Emphasis is placed on high eco-
logical trophic levels, because as we know from the modern world, predators oer the most robust signals of eco-
system complexity and food web interactions. To address how marine reptiles responded to biogeographic chan-
ges (opening of the Hispanic corridor), climate (temperature), and sea-level changes, the marine fauna from the
Paja Formation (Hauterivian-Barremian) of Colombia is being used as a model system to investigate evolutionary
patterns of top predators (i.e., origination, extinction, anatomical rates) using accurate time-calibrated phylogen-
ies. We propose a hypothesis that biotic factors will show signicant signatures to support a hotspot of high
origination rates, low extinction rates, high morphological rates of evolution, and high endemism. Preliminary
results show remarkable insights. First, the occurrence of a Colombian Barremian teleosauroid demonstrates that
the thalattosuchian teleosauroid lineage, thought to be extinct, survived the Jurassic / Cretaceous extinction.
With a body length of 9.6 m, this specimen is one of the largest known teleosauroids and the youngest known for
the lineage. is nding supports the hypothesis that tropical water temperature played an important role in con-
trolling the diversity and distribution of these large marine predators. Second, the descriptions of ichthyosaur ma-
terial reveal the rst hypercarnivore ichthyosaur from the Cretaceous, which opens up questions about food web
structures for Jurassic-Cretaceous ecosystems. Finally, a 3D surface scan of a pliosaur from the Paja Formation
reveals numerous cranial autapomorphies, which provide distinguishable information to place this new genus in
a taxonomic and systematic context and to evaluate its phylogenetic and paleobiogeographic relevance. While
most pliosaurs were certainly extinct by this time, the clade including Kronosaurus and Brachauchenius survived
well into the Late Cretaceous, thus the evaluation of this sauropterygian material from the same rocks suggests
the Paja Formation of Colombia may be where some of the last pliosaurs and rst elasmosaurs ever known occur.
is project will set the stage for continued explorations of large-scale patterns in species diversity for other
taxonomic levels for a better understanding of the consequences of the Jurassic-Cretaceous extinction on marine
vertebrate faunas, and ultimately of the advent of today´s marine ecosystems.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
Morphological analysis of a nectridean lepospondyl,
Diceratosaurus, from Linton and Five Points, Ohio
Jamey H.M. Creighton1 and Jason S. Anderson2
1Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada;
2Department of Comparative Biology & Experimental Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary,
AB, T2N 4N1, Canada;
Lepospondyli is a group of small-bodied tetrapods traditionally including ve Paleozoic groups: Microsauria,
Lysorophia, Nectridea, Aistopoda, and Adelosondyli, united by the presence of elongate trunks and holospon-
dylous vertebrae. However, more recent studies have shown these taxa show few consistent similarities and are
likely a polyphyletic assemblage. For example, recent analyses have placed aïstopods deep on the tetrapod stem
(with animals showing a progression from ‘sh’ to terrestrial tetrapod features) and Lysorophia and Microsauria
(in part) with amniotes. Nectridea, which is thought to be quite basal in the early tetrapod phylogeny, has not
yet been included in some of these studies. More information needs to be collected to test the interrelationships
of nectrideans among early tetrapod groups. is study focuses on Diceratosaurus, a nectridean solely known
from Linton and Five Points, Ohio. Latex peels of the skull roof and the palate are being analyzed and illustrated
by using photography and light microscopy. Preliminary results suggest that Diceratosaurus comprises two dis-
tinct morphs that altogether range from 14–25 cm in skull length: a broad, round-snouted morph, and a small,
narrow-snouted morph which has never been seen in nectrideans before. We test several hypotheses to explain
this variation including ontogenetic change, polymorphism, and the presence of multiple species. Examining the
smallest specimens, which are the narrow-snouted morphs, to the largest specimens which are the broad-snouted
morphs, there seems to be no signs of an ontogenetic dierence; the dermal ornamentation is organized with dis-
tinct pits and ridges, all bones in the skull roof are ossied, and the sutures are tightly closed in the smaller nar-
row-snouted morphs. is is not what one would expect if this were a juvenile form of Diceratosaurus. Although
more work remains to be done documenting the anatomy of the palate, there are dierences in the bones of the
pre-orbital region of the skull and in the ornamentation around the tabular horn region. We believe multiple spe-
cies to be the most likely explanation. e discovery of a second morph and these results could further support
the conclusion that not only nectrideans, but lepospondyls as a group, are more diverse than originally thought.
Vertebrate Anatomy Morphology Palaeontology 9:139
A morphometric analysis of the turtle manus and its
implications for the palaeoecology of extinct turtles
omas W. Dudgeon1,2, Marissa C.H. Livius3, and Jordan C. Mallon3,4
1Department of Ecology and Evolutionary Biology, University of Toronto, 27 King’s College Circle, Toronto, ON M5S 1A1,
Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, ON, M5S 1C6, Canada
3Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Herzberg Laboratories, Ottawa, ON, K1S 5B6,
4Beaty Centre for Species Discovery and Paleobiology Section, Canadian Museum of Nature, P.O. Box 3443, Station D,
Ottawa, ON K1P 6P4, Canada;
Among the most widely used predictors of palaeohabitat in fossil turtles is the skeletal proportions of the
forelimb (humerus:ulna:manus), yet its application has been criticized on the grounds that the ternary dia-
grams used to represent those proportions neither control for phylogenetic eects, nor provide statistical
likelihood estimates for palaeohabitat assignment. In this study, we apply linear statistical modeling to in-
vestigate the relationship between forelimb proportions and habitat among turtles, and use them to infer the
palaeohabitats of problematic fossil species. We performed three morphometric analyses: the rst focusing on
the major components of the forelimb (humerus, ulna, and manus), the second on the manus proper (meta-
carpals, phalanges, and unguals), and the third combining these two datasets (humerus, ulna, metacarpals,
phalanges, unguals). For each of these datasets, we used phylogenetic generalized least squares regression to
extract the residuals for subsequent analysis, which are corrected for both size and the phylogenetic non-in-
dependence of taxa. Each set of residuals was subjected to a linear discriminant analysis (LDA) to determine
the predictive accuracy of these measurements on habitat, which was divided into the following six bins: ‘all
bodies of water’, ‘moving or large bodies of water’, ‘primarily on land’, ‘primarily on land often in water’, ‘pri-
marily on land seldom in water’, and ‘stagnant or small bodies of water’. We then used the discriminant func-
tions to predict the palaeohabitats of the extinct Basilemys variolosa, Palaeochersis talampayensis, Proganochelys
quenstedti, Eunotosaurus africanus, and Odontochelys semitestacea. e manual dataset and combined forelimb
and manual dataset performed similarly well, with classication accuracies of approximately 82% and 83%,
respectively. e forelimb dataset performed poorest, with a classication accuracy of just 72%. Based on these
analyses, Basilemys variolosa is resolved as a fully terrestrial turtle that preferred dry environments with well-
drained substrates; Palaeochersis talampayensis and Proganochelys quenstedti are similarly recovered as highly
terrestrial; Eunotosaurus africanus was likely primarily terrestrial, occasionally venturing to the water; and
Odontochelys semitestacea was likely semi-aquatic, spending signicant periods of time both on land and in the
water. Taken together, these results suggest that manual proportions provide a particularly powerful habitat
proxy in turtles, and provides still further evidence that stem turtles were primarily terrestrial in nature.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
A new plastomenine trionychid (Testudines: pan-
Trionychidae) from the Milk River Formation of
Southern Alberta (Cretaceous: Santonian)
Shauna C. Edgar1, Don B. Brinkman2, Michael J. Ryan3, and David C. Evans1,4
1Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2,
2Royal Tyrrell Museum of Palaeontology, P.O. Box 7500, Drumheller, AB T0J 0Y0, Canada;
3Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada;
4Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, ON, M5S 1C6, Canada;
e pre-Campanian trionychid fossil record in North America comprises highly fragmentary specimens, which
are often not identiable beyond Pan-Trionychidae. Here, we describe a new species of plastomenine soft shell
turtle based on a partial carapace and plastron (ROM 56647) from the Santonian Milk River Formation of
southern Alberta, dated at approximately 84 Ma. Plastomeninae is characterized by the complete suturing of the
plastral bones along the midline, a crescent-shaped entoplastron, and enlarged eighth costals. ROM 56647 has
a unique combination of plastomenine characters (i.e., midline contact of posterior plastral elements, dorsoven-
trally long eighth costal) and apomorphies (emarginate nuchal, enlarged tubercles on the carapace, wide pygal
notch with a straight anterior edge, and fused hyo-hypoplastron) that allows us to identify it as a new taxon.
Phylogenetic analysis using parsimony places the new taxon within Plastomeninae as the sister taxon to a clade
containing Plastomenus, Helopanoplia and Hutchemys. is phylogenetic position implies that Aspideretoides fo-
veatus, Atoposemys, and Gilmoremys, all of which have a more basal position within Plastomeninae, and had ghost
lineages extending at least to the Santonian. As the oldest pan-trionychid that can be described to the species level
in North America, the new taxon represented by ROM 56647 oers novel insights into both the early evolution
of trionychids in North America and the pre-Campanian biodiversity of turtles in what is now southern Alberta.
Life history of an archaic placental mammal,
Pantolambda bathmodon (Placentalia, Pantodonta)
Gregory F. Funston1, Paige E. dePolo1, Sarah L. Shelley1, John R. Wible2,
omas E. Williamson3, and Stephen L. Brusatte1
1School of GeoSciences, University of Edinburgh, Edinburgh, UK;
Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA
3New Mexico Museum of Natural History and Science, Albuquerque, New Mexico, USA
e rise of mammals after the extinction of the dinosaurs remains one of the most enigmatic intervals in the
evolution of mammals. A relatively sparse Paleocene fossil record and confusing interrelationships between taxa
means that little is known of the evolution, ecology, and biology of these animals. As a result, the life history
of these organisms is completely unstudied, despite likely playing a key role in the ability of these clades to
rapidly proliferate and increase in body size in recovering ecosystems. However, intensive collection eorts in
Vertebrate Anatomy Morphology Palaeontology 9:139
the San Juan Basin of New Mexico in the last decade have drastically improved the record of many Paleocene
mammals, and oer the rst opportunity to address questions about the life history of these animals. Here, we
present preliminary results of an in-depth paleohistological analysis of Pantolambda bathmodon, an early, possibly
gregarious pantodont, using an ontogenetic series of individuals. Pantodonts were bizarre, herbivorous euther-
ians of unknown phylogenetic anity, and were among the rst mammal lineages to reach large body sizes in
the Paleocene. In examining both dental and skeletal records of growth from the same individuals, including a
juvenile still bearing deciduous teeth, our study is among the most comprehensive paleohistological analyses of
any fossil mammal. is intensive approach allows for unprecedented insights into the life history of this species.
Neonatal lines in the teeth indicate that the deciduous premolars and the rst upper molar were erupted prior
to birth, similar to precocious, nidifugous mammals today. Daily incremental lines in the enamel and dentine
suggest rapid crown formation times (~45–70 days) and a gestation period of at least 15 weeks. A stress line in
the postcranial bones, recording an anomalous decrease in growth towards the end of this individual’s life, may
represent the weaning event. In the absence of geochemical evidence, it is unclear which of two stress lines in
the teeth corresponds to this event, but these lines occur roughly one and two months after birth, respectively.
e weanling perished approximately 2.5 months after birth, weighing about 17 kg. An adult individual ex-
hibiting severe wear on the dentition allows us to estimate maximum longevity in Pantolambda bathmodon at
about 7 years. In comparison with life history data on living mammals from the Paneria dataset, Pantolambda
bathmodon had a gestation length and weaning duration below average for a placental of its adult body size (42
kg), but within the range of known variation. However, its lifespan was exceptionally short, falling outside the
bounds of comparable living mammals. Together, these lines of evidence suggest a relatively rapid pace of life in
Pantolambda bathmodon, despite its relatively large body size. Ongoing sampling of more individuals and geo-
chemical analyses should allow for estimation of time to sexual maturity and help to conrm the identity of the
weaning line, completing our picture of the life history of this pioneering species.
Revisiting the sedimentology and depositional
evolution of the Cypress Hills Formation (Eocene –
Miocene) in southwestern Saskatchewan, Canada:
implications for vertebrate microfossil assemblages
Meagan M. Gilbert
Saskatchewan Geological Survey, Box 104, La Ronge, Saskatchewan, S0J 1L0
e Eocene to Miocene Cypress Hills Formation (CHF) spans 28 million years, and forms the conglomeratic
caprock of the Cypress Hills plateau in southwestern Saskatchewan. e formation records one of the last major
sedimentation events in the western plains of North America at a time when the world was undergoing major
climate uctuations. As well, the CHF contains the only high latitude, non-polar mammalian fossil assemblage
known (Uintan to Whitneyan land mammal stages) in North America. Several palaeontologic studies have large-
ly focused on taxa recovered from vertebrate micro and macrofossil sites, which have shed light on diversity and
faunal turnover during this critical time. In contrast, the CHF has been the focus of few detailed geologic studies,
reected in the relatively poor constraint on the regional stratigraphy and timing of depositional events. Recently
a eld program has been underway to establish a depositional model for the CHF immediately north of Eastend,
Saskatchewan augmented by fauna recovered from vertebrate microfossil sites. Preliminary results have illustrated a
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
complex network of multi-episode cut-and-ll braided channel deposits and their associated channel bars and ood-
plains. is complexity has serious implications for understanding the stratigraphic relationships between fossil sites
and the strata they are recovered in, particularly regarding vertebrate microfossil assemblages. is ongoing study
highlights the importance of high-level sedimentology and stratigraphy for understanding fossil assemblages in time
and space, and will provide invaluable context for future paleontologic work undertaken in the region.
Dinosaur fossil discovery using remotely piloted
aircra systems and spectral mixture analysis
Sean Herridge-Berry1, Caleb M. Brown2, Derek R. Peddle1, Brian J. Pickles3,
and Craig A. Coburn1
1Department of Geography & Environment, and Alberta Terrestrial Imaging Centre (ATIC), University of Lethbridge,
Lethbridge, AB, T1K 3M4, Canada;;;
2Royal Tyrrell Museum of Palaeontology, P.O. Box 7500, Drumheller, AB, T0J 0Y0, Canada;
3School of Biological Sciences, University of Reading, Whiteknights, Reading, RG6 6EX, UK;
Prospecting for new fossil sites remains an integral part of palaeontological research. Given that fossil discov-
eries generally rely on exposed bedrock, the most productive areas are often associated with similar geophysical
features, including low vegetation cover, high topographic relief, and high rates of erosion, such as badlands,
deserts, and/or Arctic outcrop. ese regions also tend to have limited transportation infrastructure, are remote
and rugged, and can be geographically extensive in area, posing limitations to terrestrial access. Given these limit-
ations, potential fossil-bearing areas may represent prime areas for remote sensing where imagery can be collected
in a relatively short amount of time from platforms such as satellites, airplanes, helicopters, or remotely piloted
aircraft systems (RPAS, a.k.a. drones). e sensors aboard these platforms measure the amount of solar radiation
in dierent wavelengths as reected by the ground surface to provide information about the unique reectance
patterns of the target. ese technologies have revolutionized the acquisition of large-area georeferenced imagery
useful for ecological interpretation and resource exploration. ey may have utility in detecting exposed fossil
resources that are indicative of a larger area (10–100 m), high-density (10–100 bones/m2) accumulations of large
bones, representing monodominant or multi-taxic bonebeds. To date, the use of these aerial platforms in palae-
ontology has been minimal, and when used, has been restricted to mapping known fossil occurrences – primarily
trackways such as in Petti et al. (2018). However, it remains to be tested if, and to what extent, remote sensing
can perform in the original detection of these extensive fossil resources.
is research represents a laboratory and eld-based proof-of-concept test for the remote sensing of fossil re-
sources, specically vertebrate bonebeds, using the Campanian-aged Dinosaur Park Formation (DPF), Dinosaur
Provincial Park, Alberta, as a case study. e markers used in this study include weathered fossil bones and
modern lichen colonies (Xanthoria sp.), which may preferentially colonize fossil bone relative to other substrates.
Fossil bones can possess diverse microbial communities (Saitta et al. 2019), and a study of Antarctic Eocene
fossils revealed colonisation by several lichen species (García et al. 2020). Distinct geological features such as
palaeo-channels and point bar deposits may also represent markers to be detected.
Due to the small size of most fossil targets, Spectral Mixture Analysis (SMA), an advanced image process-
ing technique, is being investigated as a sub-pixel scale analytical approach following some of the key SMA
protocols developed by Peddle and Smith (2005). To test this, high-resolution spectral measurements of these
characteristic fossil targets were collected in a controlled laboratory setting at the Alberta Terrestrial Imaging
Centre (ATIC). Fossils, lichen-covered fossils, and geologic samples were loaned from the Royal Tyrrell
Vertebrate Anatomy Morphology Palaeontology 9:139
Museum of Palaeontology (RTMP) and provided representative examples of targets found from DPP for spec-
tral measurement at ATIC.
Spectral measurements were acquired in the ATIC Remote Sensing Lab at the University of Lethbridge using
an Analytical Spectral Devices (ASD) Fieldspec-3 Full-Range Spectroradiometer (350–2500 nm). Spectra to de-
rive reectance were acquired with reference to a calibrated white Spectralon panel (pressed polytetrauoroethyl-
ene — PTFE). e spectra were post-processed and adjusted to account for multi-detector noise at sensor bound-
aries of 1000 nm and 1900 nm. Amongst the samples, there were four distinct patterns of reectance: fossil bone,
sediment, modern lichen, and teeth. is shows that these representative targets are suciently dierent spec-
trally and suitable for input to SMA for spectral separation with pixel-scale targets. ese data provide a basis for
laboratory spectral analysis and as a planned input for SMA of imagery from RPAS missions (described below).
For example, we expect that the unique reectance signatures of fossil bone and teeth, sediment, and lichen are
suitable endmember spectra for input to SMA.
In September 2020, eld deployment of a RPAS took place at DPP with ATIC, RTMP and Alberta Parks sta,
and following COVID-19 protocols. Five sites were imaged at two altitudes (30 m and 100 m above ground
level, or AGL) using two camera systems. Multispectral images were acquired using a MicaSense RedEdge-M
ve-band camera, with simultaneous RGB images acquired using a DJI X4S gimble-mounted camera. e
multispectral camera captured images in ve bands allowing data to be collected from the blue, green, red,
near-infrared, and red-edge areas of the electromagnetic spectrum while the RGB camera acquired images in the
blue, green, and red portions of the spectrum. After images were mosaicked using stitching procedures in Pix4D
software, the resulting images had nominal ground sample distances as small as 0.8 cm at 30 m AGL.
Based on analysis of these remote sensing lab and RPAS products to date, the high spatial resolution imagery
combined with the spectroradiometer data provides appropriate inputs to SMA. Using these data and algorithms
together oers new opportunities for detecting fossil resources in the DPF and may have utility in other similar
but more remote, extensive, and challenging fossil-bearing outcrops.
Literature Cited
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mains from Antarctica. Polar Biology 43:2011-2019. DOI 10.1007/s00300-020-02761-9
Peddle, D.R., and A.M. Smith. 2005. Spectral mixture analysis of agricultural crops: Endmember valida-
tion and biophysical estimation in potato plots. International Journal of Remote Sensing 26:4959-4979. DOI
Petti, F.M., M. Petruzzelli, J. Conti, L. Spalluto, A. Wagensommer, M. Lamendola, R. Francioso, G. Montrone, L. Sabato,
and M. Tropeano. 2018. e use of aerial and close-range photogrammetry in the study of dinosaur tracksites: Lower
Cretaceous (upper Aptian/lower Albian) Molfetta ichnosite (Apulia, southern Italy). Palaeontologia Electronica 21:1-
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Saitta, E.T., R. Liang, M.C.Y. Lau, C.M. Brown, N.R. Longrich, T.G. Kaye, B.J. Novak, S.L. Salzberg, M.A. Norell, G.D.
Abbott, M.R. Dickinson, J. Vinther, I.D. Bull, R.A. Brooker, P. Martin, P. Donohoe, T.D.J. Knowles, K.E.H. Penkman,
and T. Onstott. 2019. Cretaceous dinosaur bone contains recent organic material and provides an environment condu-
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Canadian Society of Vertebrate Palaeontology 2021 Abstracts
Feeding ecology of the Bearpaw Formation mosasaur
Femke M. Holwerda
Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, T0J 0Y0, Canada;
e Campanian sediments of the Bearpaw Formation yield a rich marine fauna from the northern exposures of the
Western Interior Seaway. Many well-preserved mosasaur skeletons, representing most of the mosasaur taxa from this
geological unit in Alberta, including skulls and dentition, are housed at the Royal Tyrrell Museum of Palaeontology.
Good preservation of tooth-bearing bones not only allows for the study of tooth morphology, but also for analysis
of dental microwear, or microscopic wear on dental surfaces, generated by tooth-tooth or tooth-food occlusion/abra-
sion, and geochemical analyses. Microwear is categorized as small scratches, large scratches (gouges) and pits.
e three most common mosasaurs from the collections were sampled for two-dimensional microwear:
Mosasaurus missourensis, Prognathodon sp., and Plioplatecarpus primaevus. e most common and large mosa-
sauroids, Mosasaurus and Prognathodon, show dierences in microwear between their upper and lower jaws.
Mosasaurus missourensis shows a high total and average number of small scratches in the premaxillary and max-
illary teeth, and a low number in the dentary. Prognathodon sp. shows a large amount of pits in both upper and
lower tooth rows, and a high number of gouges in the maxilla. As scratches indicate feeding on softer prey, and
gouges show feeding on harder prey items, this could already reveal a dierence in feeding ecology between these
two large mosasaurs.
Teeth of the less common and smaller Plioplatecarpus primaevus also show a high average number of gouges
and pits, in contrast to its small piscivorous tooth morphology. is could indicate regular feeding on ammon-
ites and belemnites for this taxon.
Using Energy-Dispersive X-ray Spectroscopy (EDX) analysis as another independent line of evidence of mosa-
saur feeding in the Alberta Bearpaw Fm., the elements strontium, calcium and barium are measured on isolated
teeth. Mosasaurus missouriensis plots on the resulting PCA scatterplot together with elasmosaurid plesiosaurs,
hybodont and Cretodus sharks, indicating mainly piscivory and sarcophagy. Prognathodon sp. mainly plots togeth-
er with sawsh, indicating durophagy. Finally, Plioplatecarpus plots away from both of the larger mosasaurs, and
overlaps with hybodont sharks, possibly indicating piscivory.
is study hints at an ecient level of niche partitioning amongst the mosasaurs of the northern Western
Interior Seaway. A follow-up study using isotopes and three-dimensional microwear analysis will seek to
conrm these ndings.
Vertebrate Anatomy Morphology Palaeontology 9:139
Osteohistology of a thescelosaurid (Dinosauria,
Ornithischia) bula from the Wapiti Formation
(Campanian) of Northern Alberta: implications for
diversity of growth strategies and osteohistological
features within escelosauridae
Michael Naylor Hudgins1, Phil R. Bell2, Nicolás E. Campione2,
Federico Fanti3, Robin L. Sissons1, Matthew J. Vavrek4, Derek W.
Larson, and Corwin Sullivan1,6
1Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada;;;
2School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia; pbell23@;
3Dipartimento di Scienze della Terra e Geologico-Ambientali, Alma Mater Studiorum, Università di Bologna, 40216
Bologna, Italy;
4Cutbank Palaeontological Consulting, Grande Prairie, AB, T8W 0H6, Canada;
5Royal British Columbia Museum, Victoria, BC, V8W 9W2, Canada;
6Philip J. Currie Dinosaur Museum, Wembley, AB, T0H 3S0, Canada
Bone histological studies have provided detailed information about the diversity of, and variation in, growth
strategies, life history, and behaviour in non-avian dinosaurs. However, only a few osteohistological (i.e., analyses
focusing on the microscopic structure and function of bones) analyses of escelosauridae have been conducted.
Here we present new histological data from a partial bula (UALVP 50999) of a thescelosaurid from the late
Campanian (~73.5 Ma) Wapiti Formation of northern Alberta. e partial bula consists of well-vascularized
brolamellar and parallel-bred bone with longitudinal and lamellar vasculature, as well as primary and second-
ary osteons, throughout. Extensive secondary remodeling occurred on the posteromedial margin of the section,
likely due to biomechanical stresses from locomotion as the animal grew. Seven lines of arrested growth (LAGs)
were deposited, suggesting that the individual was at least seven years old at the time of death. e individual
likely reached sexual maturity based on prior growth models of reptilians and dinosaurs, although this is dicult
to determine with certainty. e onset of sexual maturity in UALVP 50999 coincides with bone texture changes
from the inner to outer cortex, and growth deceleration reected in narrowing inter-LAG spaces towards the
periosteum. However, the individual had not reached skeletal maturity at the time of death, based on extensive
secondary remodeling and the absence of an external fundamental system. is inference is consistent with prior
research indicating that dinosaurs reached sexual maturity before skeletal maturity. e histology of the partial
bula suggests that the growth rate of the Wapiti thescelosaurid was similar to that of Haya, Jeholosaurus, and
Oryctodromeus, and faster than that of Orodromeus, but slower than that of Hypsilophodon and derived ornithis-
chians. In UALVP 50999, an interval of rapid growth appears to have taken place following deposition of the
fth LAG, although growth abruptly slowed again with deposition of the last two LAGs. Some specimens of
Haya and Jeholosaurus show evidence of a similar growth pattern, involving ‘moderate’ growth in early life,
followed by a period of rapid growth, and then slow growth later in life. However, the increases and decreases in
growth rate inferred from UALVP 50999 may also indicate changing environmental conditions, niche partition-
ing between juveniles and adults, or random variation in the individual’s growth rate. e skeletal immaturity
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
of UALVP 50999 adds to the evidence, from previous histology-based age estimates for other taxa, that most
small-bodied ornithischian specimens in the fossil record represent individuals that did not live to reach skeletal
maturity. Whether this pattern results from an r-selected reproductive strategy in thescelosaurids, a taphonomic
bias, or a random signal is unclear. A larger histological data set is necessary for future research addressing a range
of fundamental questions pertaining to thescelosaurid palaeobiology, but the present analysis represents a step
towards this goal and provides evidence that should prove useful in future studies of bone tissue variation and
diversity of growth strategies among small-bodied ornithischians in general.
Impacts of Miocene tectonism and climate change
on diversity dynamics of carnivoran and ungulate
mammals in North America
Blue Hunter-Moatt1, and Danielle Fraser2
1Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6;
2Palaeobiology, Canadian Museum of Nature, PO Box 3443 Stn “D”, Ottawa ON K1P 6P4;
Across modern landscapes, tectonically active, topographically complex environments (e.g., mountain ranges)
support greater mammalian biodiversity than tectonically quiescent lowlands at the same latitude. One possible
explanation for topographic diversity gradients is that tectonic processes promote diversication of mammals by
increasing habitat heterogeneity. Additionally, climate warming may increase species richness in mountainous re-
gions as lowland taxa track their climatic niche to higher elevations. In this study, we assess the inuence of land-
scape evolution, involving both tectonic and climatic change, on the diversity dynamics of Miocene carnivoran
and ungulate faunas in North America. Using Capture-Mark-Recapture (CMR) methods and fossil occurrence
data from the MioMap database, we calculated origination and extinction rates of carnivoran and ungulate spe-
cies in ve North American study regions with unique landscape histories.
CMR involves repeatedly sampling, marking, and releasing organisms thus creating an “encounter history” for
each individual. In palaeobiology, occurrences of fossil species divided among discrete time bins comprise the
encounter histories that are used to estimate the number of species present in each time bin, sampling probabil-
ities, and diversication rates. ree regions, the Columbia Basin, the Rocky Mountains, and the Southwest (i.e.,
California, Arizona, New Mexico, Nevada), were tectonically active during parts of the Miocene. Two regions, the
Great Plains and the Gulf Coast, were tectonically quiescent. We did not detect pulses of origination coincident
with tectonic events in any active region, contra to our prediction. However, we found extinction peaks in the
Rocky Mountains and Southwest during the Middle Miocene Climate Optimum. is is consistent with extinc-
tion of high elevation taxa during global warming, which is predicted for numerous high latitude taxa today. We
used biogeographic stochastic mapping to test for rates of dispersal among regions and found that biogeographic
processes during the Miocene were dominated by dispersal of species from the Great Plains to other study regions
likely reecting habitat tracking during climate change. Together, these results suggest that interactions between
climate change and topographic complexity inuence mammalian dispersal and extinction dynamics, but that
tectonic activity alone has not promoted speciation of large mammals at least in North America.
Vertebrate Anatomy Morphology Palaeontology 9:139
New material of the oldest metamorphic salamander
(Amphibia, Urodela) from the Middle Jurassic of
China yields insights into palaeoecological disparity
Jia Jia1,2,3, Jason S. Anderson3, and Ke-Qin Gao1
1School of Earth and Space Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China;;
2State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS), 39 East
Beijing Road, Nanjing, Jiangsu Province, 210008, China
3Department of Comparative Biology and Experimental Medicine, University of Calgary, 3330 Hospital Drive, Calgary,
AB, Canada, T2N 4N1;
Salamanders (total-group named Caudata; crown-group named Urodela) are a group of extant tailed amphib-
ians that are ecologically diversied with individuals at adult stage living in water (aquatic), on land (terrestrial),
in a tree (arboreal) or migrating between water and land (semiaquatic). How and when these ecological prefer-
ences dierentiated among salamanders remains unclear because of a poor fossil record. e origin of Caudata
was estimated by molecular studies to have occurred during the Late Paleozoic, whereas the geologically old-
est salamander Triassurus sixtelae was documented from the Middle/Late Triassic (~230 Ma) in southwestern
Kyrgyzstan. e next oldest known fossil records of salamanders are found from the Middle Jurassic Bathonian
(~168–166) in several localities of Eurasia (UK, Russia, Kyrgyzstan and China). Most of these Middle Jurassic,
and the only known Triassic, salamanders are stem members of Urodela as evidenced by the absence of the spinal
nerve foramina in the atlas that characterize Urodela. Only ve contemporary taxa have been found as basalmost
urodeles, including Kiyatriton krasnolutskii from Siberia, Russia; ‘Kirtlington salamander B’ from Kirtlington,
UK and three taxa (Chunerpeton, Jeholotriton and Liaoxitriton daohugouensis) from the Daohugou fossil locality in
northern China. e morphological evolutionary histories of early salamanders are insuciently understood be-
cause most Middle Jurassic or earlier taxa are represented either by immature specimens (Triassurus) or fragmen-
tary/disarticulated bones (e.g., K. krasnolutskii), but the three taxa from China are represented by complete and
articulated skeletons. Moreover, patterns of palaeoecological disparity among early salamanders remain unclear
because all stem-group and most crown-group urodeles are neotenic, except Liaoxitriton daohugouensis, which
represents the oldest known metamorphic salamander as evidenced by its moderate size, absence of internal and
external gills, anterolaterally oriented palatal ramus of pterygoid, and extensively ossied limb structures.
To date, Liaoxitriton daohugouensis is known from three specimens from the Middle Jurassic Haifanggou Formation at
the Daohugou fossil locality, Inner Mongolia, China. It was originally misclassied as congeneric with the Early Cretaceous
Liaoxitriton zhongjiani from the Yixian Formation at the Xintaimen fossil locality, Liaoning Province, China, but this attri-
bution raised doubts. Here we report a new, complete, and almost fully-grown specimen from the type locality. Micro-CT
scanning and visual examination reveal details of the dermal skull roof, suspensorium, braincase, mandible, autopodium,
and tail that were previously unclear. Five autapomorphies of this taxon are identied, including: parietal elongate; palatal
process of pterygoid expanded; vomer expanded posteriorly, reaching close to anteroposterior ventral midpoint of cranium;
cultriform process of parasphenoid shortened anteroposteriorly; and scapular blade shortened to slightly more than one-
half width of coracoid. Our cladistic analyses based on a data matrix of 108 morphological characters (24% newly iden-
tied) and 22 taxa nd that “L. daohugouensis” is crownward of Linglongtriton and is not the sister taxon to L. zhongjiani,
which enable us to transfer “L. daohugouensis” into a new genus. Our results further identify “L. daohugouensis” and several
Mesozoic taxa including Linglongtriton, Liaoxitriton sensu stricto, Nuominerpeton and Regalerpeton from northern China
as stem members of the Asiatic salamander family Hynobiidae, and therefore predates the origination time of Hynobiidae
previously estimated by molecular studies by at least 8 Myr.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
e new specimen of “L. daohugouensis” has a wrinkled caudal n and several features commonly seen in extant
terrestrial hynobiids, including anteroposteriorly short skull, rounded snout, many vomerine teeth with vomerine
teeth rows spanning most of the transverse dimension of the palate, and extensively ossied limb. e combin-
ation of these features suggests “L. daohugouensis” is a semi-aquatic at adult stage, a previously unknown pala-
eoecological preference among Mesozoic salamanders. Comparisons with both contemporary taxa (Chunerpeton
and Jeholotriton) and other stem hynobiids, including the metamorphic and terrestrial Nuominerpeton and the
neotenic Regalerpeton suggest that both life history strategies and ecological disparities have taken place by the
Middle Jurassic Bathonian stage among urodeles.
is research was supported by National Science Foundation of China grants NSFC 41702002 and 41872008; and the
State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS) 193111.
Vertebrate diversity trends and chrono-, litho-, chemo-,
and cyclostratigraphy of the Late Cretaceous Manitoba
Escarpment in Saskatchewan and Manitoba, Canada
Aaron A. Kilmury1, Michelle P.B. Nicolas2, and Kirstin S. Brink1
1Department of Geological Sciences, University of Manitoba, Winnipeg, MB, Canada;;
2Manitoba Geological Survey, Winnipeg, MB, Canada;
Stratigraphic correlations of Late Cretaceous Western Interior Seaway (WIS) deposits of the Manitoba escarp-
ment with coeval deposits across North America have proven historically challenging due to poor surface expos-
ures and the repeating nature of calcareous and non-calcareous, massive mudstone units bound by unconform-
able contacts. Stratigraphic work over the last two decades, including an improved lithostratigraphic framework,
radiometric ages of several horizons, chemostratigraphic proles of drillcore, and timing and duration estimates
of transgressive-regressive mega cycles, have signicantly improved the accuracy of regional correlations. A cor-
relation chart consisting of several types of stratigraphic proles was constructed and correlated with recently
estimated trends of vertebrate generic diversity in order to provide insight into potential relationships between
changes in relative sea level and vertebrate diversity over a broad temporal range (Cenomanian-Maastrichtian)
from a biogeographically important, north-central locality along the WIS eastern margin.
Transgressive-regressive mega cycles are recognized in the litho- and chemostratigraphic proles of the Upper
Cretaceous deposits in Manitoba. Deposition of lithologic units with the highest estimates of vertebrate generic
diversity, the Cenomanian Belle Fourche and early Campanian Pembina members, respectively coincide with an
unnamed mega cycle referred to here as the Belle Fourche mega cycle and the Claggett mega cycle. A signicant
change in community structure is also apparent between the shark-dominated communities of the Belle Fourche
Mbr and the marine reptile-dominated communities of the lower Pembina Mbr. Dierences of average water depth
between the mid-Cenomanian and early Campanian WIS could partially explain the apparent change in vertebrate
community structure. Other likely contributing factors to the dierence in community structure include the feeding
habits of apex predators, with mainly piscivorous sharks and pliosaurs dominant in the mid-Cenomanian and mosa-
saurs with comparatively more diverse feeding habits dominant in the early Campanian. Taken together, these data
are helping to elucidate the dynamics of community structure in the WIS through time.
Vertebrate Anatomy Morphology Palaeontology 9:139
e internal cranial anatomy of Panoplosaurus mirus
(Dinosauria: Nodosauridae)
Marissa C.H. Livius1, Hillary C. Maddin1, Michael J. Ryan1, 2, and Jordan
C. Mallon1, 3
1Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Herzberg Laboratories, Ottawa, ON, K1S
5B6, Canada;;;
2Palaeobiology Section, Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, ON, K1P 6P4, Canada
3Beaty Centre for Species Discovery and Palaeobiology Section, Canadian Museum of Nature, PO Box 3443, Station D,
Ottawa, ON, K1P 6P4, Canada;
e heavily armoured and hyperossied skulls of ankylosaurs have presented challenges for the description of
their internal anatomy which is, therefore, poorly known. e quality of data that can be obtained using comput-
ed tomography (CT) imaging has increased in recent years, providing a valuable tool for examining endocranial
features that are otherwise inaccessible. Even so, highly detailed endocranial descriptions are available for only
a very few ankylosaurid ankylosaurs; data for the sister clade, Nodosauridae, are also scarce. Here we present a
digital reconstruction and description of the holotype skull for Panoplosaurus mirus (CMN 2759) and compare it
to published data for other ankylosaur taxa. Preliminary results reveal that the endocast of CMN 2759 exhibits a
less pronounced exure between the main structures of the brain (forebrain, midbrain, and hindbrain) than has
been reported in other nodosaurids and more closely resembles those of ankylosaurids. We also found convoluted
nasal passages with distinct rostral and caudal loops that correspond to those described for the nodosaurid speci-
men ROM 1215 (variably attributed to Panoplosaurus or Edmontonia). Similarly convoluted nasal passages have
also been described for the basal nodosaurid Pawpawsaurus campbelli. Although the nasal morphology of CMN
2759 is not as complex as that of the ankylosaurid Euoplocephalus tutus, this specimen demonstrates that highly
sophisticated nasal passages were also present and more complex in nodosaurids than previously reported. ese
ndings provide the rst insights into the endocranial anatomy of Panoplosaurus mirus, and will facilitate com-
parisons with other ankylosaurs to assess both systematic and paleobiological trends within Ankylosauria.
First record of a parasaurolophin hadrosaur from the
Oldman Formation of southern Alberta
Bradley D. McFeeters1, David C. Evans2,3, Michael J. Ryan1, and Hillary C. Maddin1
1Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada; bradleymc-;;
2Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, ON, M5S 2C6, Canada
3Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2,
Hollow-crested hadrosaurs (Hadrosauridae: Lambeosaurinae) are well represented in the Dinosaur Park
Formation of Alberta, but are poorly known from older units, including the underlying Oldman Formation
(Upper Cretaceous: Campanian). A new braincase from the Comrey sandstone (middle unit) zone at the Milk
River Ridge Reservoir locality in southern Alberta represents the rst diagnostic cranial material of an adult
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
lambeosaurine from the Oldman Formation. It shares with other lambeosaurines an anteroposteriorly short
parietal and short supraoccipital-exoccipital shelf. Derived characters shared with Parasaurolophus include a
thickened and steeply angled frontonasal contact, and the wide angle of the anterior frontals without a median
cleft, allowing for the identication of the rst denitive record of Parasaurolophini in the Oldman Formation.
However, in contrast to a previously described adult Parasaurolophus braincase from the Dinosaur Park
Formation, the nasal contact of the frontal lacks the pronounced posterodorsal extension that underlies the pos-
teriorly projecting crest. e posterior margin of the contact has only a small vertical projection, resembling the
condition described in juvenile Parasaurolophus, despite the large size and fused interfrontal contact of the Milk
River Ridge Reservoir braincase, indicating its adult ontogenetic status. is dierence may be attributable to
heterochrony, with the ancestral adult development of the nasofrontal contact being attained in the juvenile stage
of the stratigraphically higher form. As one of the stratigraphically lowest records of the clade Parasaurolophini,
the Milk River Ridge Reservoir specimen is a signicant source of new information concerning the timing and
process of this clade’s phylogenetic and morphological divergence from other derived lambeosaurines.
Palaeobiodiversity statistics and paleoenvironmental
implications of microvertebrate localities from
the Frenchman Formation (latest Cretaceous,
Maastrichtian) of Saskatchewan, Canada
Jack R. Milligan1, and Emily L. Bamforth1,2
1Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, S7N 5E2;
2Royal Saskatchewan Museum, T. rex Discovery Centre, Eastend, SK, S0N 0T0;
e latest Mesozoic rocks of Chambery Coulee in southwest Saskatchewan have oered insight into the paleo-
biodiversity and paleoenvironment leading up to the end-Cretaceous (K-Pg) mass extinction event. e late
Maastrichtian (Lancian) Frenchman Formation, coeval with the Hell Creek and Lance formations in the USA
contain a mixture of uvial-oodplain and terrestrial paleoenvironments less than 20 m below the K-Pg bound-
ary. ese strata are well-known for producing notable specimens of large trionychid turtles, as well as large
non-avian dinosaurs including a large specimen of Tyrannosaurus rex (RSM P2523.8) from Chambery Coulee.
Within the vicinity of the T. rex site, there are microvertebrate fossil localities that contain an assemblage of taxa
useful in paleoecological studies. Here we present the alpha and beta diversity statistics from several microverte-
brate sites found within Chambery Coulee including the ‘Kangaroo Down,’ ‘Bingo,’ ‘Hairpin,’ and ‘West-point’
sites. Analysis of the sedimentary stratigraphy and biodiversity statistics were integrated together to determine
the paleobiodiversity patterns of these microvertebrate sites and how the paleoenvironment reects patterns of
diversity at the regional level of Chambery Coulee immediately prior to the K-Pg mass extinction event. A ~9.5
m stratigraphic section at the Kangaroo Down site was correlated with previously studied sections at Hairpin,
Bingo, and West-point. e Kangaroo Down and Bingo sites are higher in section than the Hairpin and West-
point sites with the former being interpreted as low energy inland uvial environments and the latter being inter-
preted as higher energy coastal environments. Raw abundance data were used to calculate alpha diversity indices
including Chao-1 and Jackknife-2, and occurrence data were used to calculate beta diversity indices including
the Bray-Curtis similarity and Whittaker’s global beta diversity. When we compare the statistics of each of the
Chambery Coulee microvertebrate sites, we nd a high diversity of microvertebrates represented across all the
Vertebrate Anatomy Morphology Palaeontology 9:139
sites we studied after accounting for preservation bias and collection methods. e Kangaroo Down and Bingo
sites appear to include a high abundance and greater occurrence of terrestrial taxa including salamander and
trionychids (soft-shelled turtles), and semiaquatic taxa including Champsosaurus, whereas the Hairpin and West-
point sites seem to include a high abundance and higher occurrence of aquatic taxa including Myledaphus and
Lepisosteus. is suggests that paleobiodiversity statistics including alpha and beta diversity based on abundance
and occurrence data can be used as a probable measure for discerning microhabitats at stratigraphically similar
microvertebrate sites within a larger paleoenvironment. is will help elucidate biodiversity patterns across a wide
range of taxa in Chambery Coulee during the time just before to the K-Pg mass extinction event.
A bird coracoid from the Horseshoe Canyon
Formation (earliest Maastrichtian) of Alberta, Canada
Sydney R. Mohr1, Gregory F. Funston2, and omas A. Stidham3
1Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada;
2School of GeoSciences, University of Edinburgh, Edinburgh, UK;
3Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Verte-
brate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China;
A new fragmented left avian coracoid represents the rst conrmed avian skeletal element from the early
Maastrichtian (71.8–71.5 Ma) of the Horseshoe Canyon Formation of Alberta, Canada. is specimen also
represents one of the largest fossil bird coracoids found in the province. A number of features, including a prom-
inent acrocoracoid process and a well-dened procoracoid process, places this specimen within the Ornithurae. In
addition to several neornithine-like features, it retains numerous ornithurine plesiomorphies, and this mosaic of
traits indicates it is unlikely to represent a neornithine bird. As its fragmentary nature prevents a specic diagno-
sis, we therefore refer to it here as Ornithurine H (UALVP 59403). is specimen bears particular resemblance
to four unassigned ornithurine coracoids from other Campanian and Maastrichtian localities in North America,
all of which share numerous distinctive traits not found in other contemporaneous ornithurine coracoids. ese
include a shallow and weakly-dened triangular scapular cotyle, a humeral articular facet positioned lateral to
the scapular cotyle, and a prominent, hooked procoracoid process. However, several features including its larger
body size (~3.0 kg), a large supracoracoideus nerve foramen situated midway on the coracoid shaft, and a dorsal-
ly-projecting caudal rim of the scapular cotyle distinguish this specimen from other coracoids and indicate that
Ornithurine H likely represents a new taxon. e projecting rim of the cotyle and laterally-oriented humeral
articular facet are also present in the coracoid of the Turonian ornithurine Ichthyornis dispar, underscoring the dis-
tinct combination of features that characterizes Ornithurine H. Whereas this new specimen adds to the growing
list of North American fossil birds represented primarily by isolated and incomplete material, it nevertheless
expands on our understanding of early Maastrichtian paleobiodiversity in Alberta, and provides further evidence
of a widespread and diverse assemblage of ornithurine birds throughout the Late Cretaceous of North America.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
A quantitative analysis of morphological variation in
dentition among escelosauridae with implications
for thescelosaurid palaeoecology, macroevolution, and
microsite identication
Nathaniel E.D. Morley1, Michael Naylor Hudgins1, Caleb M. Brown2,
Philip J. Currie1, Han Feng-Lu3,4, and Corwin Sullivan1,5
1Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada;,,,
2Royal Tyrrell Museum of Palaeontology, Drumheller, AB, T0J 0Y0, Canada;
3School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China; han
4Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropolo-
gy, Chinese Academy of Sciences, Beijing, 100044, China; han
5Philip J. Currie Dinosaur Museum, Wembley, AB, T0H 3S0, Canada;
escelosauridae is a poorly studied clade of small, herbivorous ornithischians that existed from the Aptian
until the end of the Cretaceous in Asia and western North America. Although fossils of these gracile taxa are
generally rare, isolated thescelosaurid teeth are common at microfossil sites. However, due to their generalized
morphology, their teeth are easily confused with those of other contemporaneous small-bodied ornithischians.
We use twelve linear measurements to document morphometric variation among the unworn, heterodont
teeth of various thescelosaurid taxa based on teeth preserved in identiable skeletons of Haya griva, Jeholosaurus
shangyuanensis, Parksosaurus warreni, escelosaurus neglectus, escelosaurus sp. (SDSM 7210; formerly
Bugenosaura), and Zephyrosaurus scha. In a principal components analysis (PCA) of the measurements, PC1 and
PC2 accounted for 77% and 12% of the total variation, respectively. In a canonical variates analysis (CVA), CV1
and CV2 explained 73% and 12% of the separation among the groups, respectively, and an associated confusion
matrix correctly classied 92% of the teeth. is accurate confusion matrix classication holds promise for the
identication of isolated thescelosaurid teeth using morphometrics. A PERMANOVA showed statistically sig-
nicant separation among thescelosaurid taxa (F = 3.72, p(a) > 0.01). In both the PCA and the CVA, P. war-
reni, T. neglectus, T. sp. and Z. scha clustered closely together with signicant overlap among the premaxillary,
maxillary, and dentary teeth. However, the premaxillary teeth of H. griva and maxillary teeth of J. shangyuan-
ensis formed discrete clusters on the same plots. e morphometric overlap among the North American taxa (P.
warreni, T. neglectus, T. sp. and Z. scha) suggests that they may have shared similar feeding strategies and dietary
preferences. In contrast, the disparate morphologies of the Asian taxa (H. griva and J. shangyuanensis), relative
both to the North American taxa and to each other, suggest that they had divergent feeding strategies and dietary
preferences. is morphometric analysis should facilitate the identication of thescelosaurid teeth from microsites
and the testing of hypotheses on the biogeography, macroevolution, palaeoecology, and temporal distribution of
escelosauridae using microsite data.
Vertebrate Anatomy Morphology Palaeontology 9:139
New data on the distal tarsals of Ornithomimidae provided
by a partially articulated specimen from the Kaiparowits
Formation (late Campanian) of southern Utah, USA
Rachel E. Nottrodt1 and Andrew A. Farke2
1Department of Geoscience, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada; rachel.
2Raymond M. Alf Museum of Paleontology at e Webb Schools, 1175 West Baseline Road, Claremont, CA, 91711,
e ankle in non-avian theropod dinosaurs consists of the astragalus and calcaneum proximally and a distal series
of tarsal bones capping the metatarsals. Nearly all theropod taxa have only two distal tarsals, identied as distal
tarsals 3 and 4. Historically, the morphology and anatomical relationships of these distal tarsals is uncertain in
ornithomimosaurs due to lack of preservation and/or disarticulation, but even in articulated specimens, the bones
can be dicult to access. A previously undescribed, partially articulated ornithomimid hind limb fossil from the
Kaiparowits Formation (late Campanian) of southern Utah, USA, uniquely preserves both distal tarsals completely
and in articulation with their surrounding elements. is is the rst ornithomimid specimen from North America
for which the distal tarsals can be described in comprehensive detail from multiple views. Distal tarsal 3 contacts
both metatarsals II and III, whereas distal tarsal 4 contacts only metatarsal IV. Distal tarsal 4 also shows a tab-like
process that projects laterally. Comparison of the new fossil specimen with other ornithomimosaurs shows that distal
tarsals in Ornithomimosauria can be generalized as: i) paired, representing distal tarsals 3 and 4; ii) not fused to one
another or to the proximal metatarsals; and iii) proximo-distally compressed. Furthermore, tarsal morphology and
position across Ornithomimosauria vary in: i) shape of the posterior surface of distal tarsal 3; ii) antero-posterior
position of the distal tarsals relative to the proximal ends of the metatarsals; iii) extent of distal tarsal coverage of the
proximal metatarsal surfaces; and iv) presence of a lateral ange on distal tarsal 4. As the rst ornithomimid speci-
men from North America to reveal both the proximal and distal surfaces of both distal tarsals, and one of the very
few ornithomimids for which tarsal morphology can be seen in articulation from multiple views, this fossil shows
the importance of articulated specimens for tracking tarsal evolution and variation.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
New shallow snouted species of Velociraptor sheds light
on intraspecic variation in Velociraptor mongoliensis
and possible niche partitioning between species
Mark J. Powers1, Mark A. Norell2, and Philip J. Currie1
1Department of Biological Sciences, University of Alberta, CW-405 Biological Sciences Building, Edmonton AB, T6G
2E9, Canada;;
2Macaulay Curator, Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA;
Despite being some of the largest representatives of Dromaeosauridae, eudromaeosaurians were small to
medium sized predators in their respective ecosystems. Predatory adaptations such as serrated teeth, recurved
claws, and a specialized sickle claw on the end of their second pedal digit would have allowed them to ourish
in small- to medium-sized predator niches, as well as providing variability among close relatives. is makes
understanding their phylogenetic relationships and morphological disparity of utmost importance to addressing
broad scoping questions about dinosaur ecology. Unfortunately, in North America the fossil skeletons of dro-
maeosaurids are generally rare and are largely incomplete when found. is has been largely attributed to pres-
ervation biases for large-bodied animals in many depositional environments (particularly uvial systems). Strata
with dinosaur fossils in the Djadokhta Formation of Mongolia are represented by aeolian deposits associated with
sand accumulation or large dune collapses. Within this depositional environment, small-bodied vertebrates are
preserved more readily. Half a dozen skeletons, varying between 60 to 95% completeness, and numerous more
isolated specimens have been collected and assigned to Velociraptor mongoliensis. Referral of these specimens to V.
mongoliensis has been based on general morphological similarity and paleogeographical provenance and variation
has been assumed to be intraspecic without any formal analysis. e holotype of V. mongoliensis was discovered
at the Flaming Clis locality in Mongolia. However, most referred specimens come from further west, at or near
the Tögrögiin Shiree locality.
One nearly complete specimen collected from the Flaming Clis locality in 1995 (MPC-D 100/982), has
morphological features distinct from all other specimens referred to V. mongoliensis in possessing an antorbital
region of the skull (snout) that is distinctly shallow dorsoventrally. Examination of the temporal region of the
skull and postcranium, reveals at least four features distinct from other specimens referred to V. mongoliensis.
ese include an anteriorly abbreviated cerebellar fossa with an elongate olfactory canal, a lacrimal notch of the
frontal that is more vertically oriented as opposed to transverse in V. mongoliensis, a subvertical ridge on the ilium
anterodorsal to the acetabulum. is specimen has been referred to V. mongoliensis in several previous publica-
tions and its morphological dierences from V. mongoliensis specimens were suggested to be individual variation;
however, despite the striking prole of the skull of MPC-D 100/982 no tests of variation were performed.
Up to 15 linear measurements were taken from velociraptorine and non-velociraptorine eudromaeosaur-
ian maxillae — a highly complex and diagnostic element within eudromaeosaurians — to perform Principal
Component Analysis (PCA) and examine phenetic clustering within morphospace. e results show that
MPC-D 100/982 falls well outside the range of variation observed in other specimens referred to V. mongoliensis.
e degree to which MPC-D 100/982 varies from V. mongoliensis specimens is even greater than that observed
for the holotype of Velociraptor osmolskae (IMM99NM-BYM-3/3A), supporting the separation of MPC-D
100/982 on a species level. A notable linear spread of V. mongoliensis specimens in the PCA shows a positively
allometric trend, with smaller specimens plotting more negatively along PC 1 and PC 2 and may represent an
ontogenetic shift. To examine possible ontogenetic trends in V. mongoliensis further, linear regressions of individ-
ual maxillary variables with a high degree of taxonomic variance (maxillary height, anterior ramus length, antor-
Vertebrate Anatomy Morphology Palaeontology 9:139
bital fossa length, and lateral lamina height below the antorbital fossa anteriorly) were performed. ese features
show positive allometry in relation to maxillary length across Velociraptor mongoliensis specimens. MPC-D
100/982 does not t with these trends and falls well outside the 95% condence regression intervals. MPC-D
100/982 possesses a long antorbital fossa, a distinct maxillary fenestra morphology, and the most elongate (high
length/height ratio) snout of any eudromaeosaurian known. Discrete morphological characters and morpho-
metric analyses support separating MPC-D 100/982 from V. mongoliensis as representing its own distinct species.
Variation in the snouts of V. mongoliensis and the new species may have allowed them to have some overlap in
home ranges with reduced competition.
In modern terrestrial ecosystems, snout shapes are shown to often correlate to preferred prey size. is is
most notably demonstrated in canids, a clade with carnivorous members of similar size to most eudromaeo-
saurians. e advantage of snout shapes in prey capture, for canids and many other vertebrates, is supported
by functional morphology studies. Such studies have demonstrated that longer jaws are more eective for
rapid biting and limited power, whereas stout jaws perform more eciently in biting and handling. e
former being more eective at catching small-bodied, fast-moving prey, while the latter is better for taking
prey of larger body size that may put up more of a ght. Although we cannot observe the preferred prey of
eudromaeosaurians directly, we can use the principles of functional morphology relating to jaw biomechanics,
examine the faunal composition of ecosystems containing eudromaeosaurians, and make preliminary hypoth-
eses about drivers for variation in snout shape within the clade through time and space. Small-bodied verte-
brates are common in the Djadokhta Formation and the shallow condition in the rostrum of the new species
of Velociraptor may have been an adaptation for specializing on these prey items. Conversely, V. mongoliensis
possessed a deeper snout that became deeper as they grew and may have allowed members of this species to
have a more diverse diet as suggested by the ‘Fighting Dinsaurs’ specimen (a Protoceratops and V. mongoliensis
locked in combat)
Reconstructing life history of the sabre-toothed cat
Smilodon fatalis using bone histology
Ashley R. Reynolds
Royal Ontario Museum, Department of Natural History, 100 Queen’s Park, Toronto, ON, M5S 2C6, Canada, and Uni-
versity of Toronto, Department of Ecology and Evolutionary Biology, 25 Willcocks St, Room 3055, Toronto, ON, M5S
3B2, Canada;
e life history strategy (e.g., growth rate, time to maturity) of an organism is a fundamental aspect of its
biology that may be correlated with other ecological traits such as the degree of sociality exhibited by a species.
However, assessing the life history strategy of extinct vertebrates is dicult because their growth and behaviour
must be estimated using limited material, usually hard tissues. Osteohistology, the histological study of bone, is
increasingly being used by palaeobiologists to study life history strategies in extinct vertebrates (specically, assess-
ing time to maturity using growth curves), though there has historically been a heavy focus on reptiles. Studies
of mammalian osteohistology have become more common, but the rigorous mathematical methods for growth
curve reconstruction used for reptiles have not been adequately tested in any major mammalian group. e
purpose of this study was to test the viability of these methods on extant felids and reconstruct the growth of the
sabre-toothed cat Smilodon fatalis using osteohistological data. Specically, two hypotheses were tested relating to
the palaeobiology of S. fatalis: that it was not as sexually dimorphic as extant felids and that it was social.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
Age and weight data were collected from wild and captive individuals from 71 extant species in the carnivoran
suborder Feliformia, from which growth curves were calculated. Additionally, osteohistology of the extant lion
(Panthera leo) and tiger (Panthera tigris), the two extant felids closest in body mass to S. fatalis, were documented.
To conduct growth curve reconstruction for S. fatalis, 20 femora from Pit 3 of the Rancho La Brea tar pits were
thin sectioned at the minimum circumference of the diaphysis and lines of arrested growth (LAGs) were counted
and their circumferences measured. Growth curves for extant feliforms and S. fatalis were created using the best-
t model from the Richards family of growth models, as determined using the Akaike Information Criterion.
Curves generated for extant felids perform well in capturing the overall pattern of growth typical of a species
but tend to overestimate body mass at birth. Sexual dimorphism in adult body mass is common among extant
feliforms, with the predominant mode of sexual dimorphism being male-biased. e age at which adult body
mass is reached is positively associated with large adult body mass, while maximum daily growth rate (kg/day) is
negatively associated with social behaviour, such that social species like P. leo have a lower maximum daily growth
rate than solitary species like P. tigris. Collectively, these results suggest that sex dierences in body mass and
the varying correlates with growth rate should be considered in the analysis of S. fatalis growth. Osteohistology
of P. leo and P. tigris femora indicate that lines of arrested growth (LAGs) are deposited during femoral growth
and may be reliably used to determine approximate age at death and growth curves. S. fatalis femora classied as
juvenile never had more than two LAGs preserved, and adults had a variable number of LAGs greater than two.
Specimens with three or more preserved LAGs were included in a growth curve reconstruction using a mixed-ef-
fects process-error Richards growth model. ere is a large amount of variation in the adult body mass of the
sabre-toothed cat, ranging from 160 to 255 kg, suggesting that these cats may have showed a similar degree of
sexual dimorphism in body mass as extant felids. Growth periods were prolonged relative to extant big cats, with
individuals taking around ve years to reach adult body mass. Comparatively, asymptotic body mass is reached
in P. leo and P. tigris at 2.4 and 1.8 years, respectively. Maximum daily growth rates in S. fatalis are lower than in
P. leo and P. tigris. is may indicate gregarious social behaviour in the sabre-toothed cat. Additionally, such low
growth rates and long time to maturity are known to increase risk of extinction in extant animals. is should
therefore be explored as a contributing factor to the end-Pleistocene extinction of S. fatalis. Overall, this study
has produced the rst growth curve for any fossil carnivoran, and the methods used provide a framework within
which the evolution of life history strategies in felids can be examined.
Identifying competitive exclusion in the vertebrate fossil
record: lessons from early vertebrate morphometrics
Bradley Scott and Philip Anderson
101 Shelford Vivarium, 608 East Healey Street Champaign, IL 61820, USA;;
Competition with gnathostomes is the most common hypothesis for the extinction of the ostracoderms (Janvier
1996; Long 2011); however, it is not clear whether competition between clades is even testable in the fossil record
(Purnell 2001). We review dierent qualitative and quantitative methods for dierentiating competition from
alternative hypotheses of extinction and whether competition between gnathostomes and agnathans, specically,
can be rejected using the fossil record. Competition in the fossil record is often recognized by the appearance of
one taxon followed by the disappearance of another morphologically similar taxon in the same geographic region.
As one taxon increases in abundance the other taxon should decrease (Tilman 1987; Purnell 2001; Anderson et
al. 2011). Explicitly this is competitive exclusion (e.g., Krause 1986). Competitive exclusion can only include co-
existence for an ecologically brief time, because lengthy coexistence of two taxa followed by the disappearance of
Vertebrate Anatomy Morphology Palaeontology 9:139
one taxon requires cause beyond presence of the remaining taxon. e problem with hypothesizing competitive
exclusion as a cause of extinction is that patterns in the fossil record attributed to competitive exclusion are nearly
identical to extinction of an incumbent followed by invasion by a new species (replacement), unless there is ne
spatial and temporal resolution of rst and last appearance of each taxon. Character displacement (changes in
each taxon so they are less similar over time) is another method for identifying hypothetical competition between
taxa (Tyler and Leighton 2011); however, character displacement is not suitable as a test of competition as a cause
of extinction because it cannot reject predation, environmental changes or other alternative causes of extinction.
Early vertebrate fossil bearing sequences rarely possess the temporal and spatial resolution necessary to reject
replacement or coexistence between taxa, and even partially complete specimens are too rare to test for character
displacement. Even if alternatives to competition cannot be rejected, rejecting competition may still be feasible.
Methods for rejecting competition in the fossil record will rely on clear denitions of competition. One challenge
is that ecological denitions of competition are rarely explicit and are often broadly inclusive of any negative
interactions between two taxa (Tilman 1987). In order to create falsiable criteria for competition with broad
utility in this study, we constrain our denition of competition to the following: the use of the same resources
(food or habitat) by more than one taxon in the same place at the same time, distinct from predation, bioengin-
eering, or other indirect negative interactions. Under this denition, competition between two or more taxa
can be rejected if any of the following are true: 1. Taxa are not present at the same time, 2. Taxa are not present
in the same place, 3. Taxa do not use the same habitat, or 4. Taxa do not consume the same food. Identifying
criteria 1 and 2 depends on the temporal and spatial resolution of the fossil record. While criteria 3 and 4 can
never be known for certain in fossil taxa, they can be estimated using functional morphology and biomechanics.
Neontological studies have shown competition is often stronger between morphologically similar taxa and weaker
between morphologically dierent taxa (e.g. Montoya and Burns 2007; Adams 2004). If two taxa are suciently
dierent from each other, then competition can be rejected. We present preliminary morphometric analysis of
ostracoderms and early gnathostomes with discussion of how we intend to establish a standard for morphological
dierence sucient to reject competition among early vertebrates. Our standard will be based on comparison
with ecomorphology in extant sharks (Neoselache). By rejecting competition, we can focus on alternative hypoth-
eses, as well as narrow the range of taxa for which extinction due to competition is a plausible hypothesis.
Literature cited
Adams, D.C. 2004. Character displacement via aggressive interference in Appalachian salamanders. Ecology 85:3664–3670.
Anderson, P. S. L., M. Friedman, M.D. Brazeau, and E.J. Rayeld. 2011. Initial radiation of jaws demonstrated stability
despite faunal environmental change. Nature 476:206–209.
Janvier, P. 1996. Early vertebrates. Clarendon Press, Oxford, 408 pp.
Krause, D.W. 1986. Competitive exclusion and taxonomic displacement in the fossil record: the case of rodents and
multituberculates in North America; pp. 95–117 in K.M. Flanagan, and J.A. Lillegraven (eds.). Contributions to
Geology Special Paper 3, Vertebrates, Phylogeny, Philosophy. University of Wyoming, Laramie, WY.
Long, J. 2011. e Rise of Fishes500 Million years of Evolution. 2nd ed. John Hopkins University Press, Baltimore, MD, 224
Montoya, I., and K.C. Burns. 2007. Community-wide character displacement in New Zealand skinks. Journal of
Biogeography 34:2139–2147.
Purnell, M. A. 2001. Scenarios, selection, and the ecology of early vertebrates; pp. 188–208 in P.E. Ahlberg (ed.). Major
events in early vertebrate evolution. Taylor & Francis, London, UK.
Tilman, D. 1987. e importance of the mechanisms of interspecic competition. e American Naturalist 129:769–774.
Tyler, C.L., and L.R. Leighton. 2011. Detecting competition in the fossil record: support for character displacement
among Ordovician brachiopods. Paleogeography, Paleoclimatology, Paleoecology 307:205–217.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
A hesperornithiform (Avialae: Ornithuromorpha)
from the Upper Cretaceous Nemegt Formation (lower
Maastrichtian) in Mongolia
Tomonori Tanaka1, 2, Yoshitsugu Kobayashi3, Yuong-Nam Lee4, Robin Sissons5,
Michael Ryan6, Tsogtbaatar Chinzorig7, and Khishigjav Tsogtbaatar8
1Tamba Dinosaur Fossil Lab, 1110, Tanigawa, Sannan, Tamba, Hyogo, Japan;
2University of Hyogo, Yayoigaoka 6, Sanda, Hyogo, Japan
3Hokkaido University Museum, Kita10, Nishi 8, Sapporo, Hokkaido, Japan;
4Seoul National University, Bldg #25-1, Rm #510, 1 Gwanak-ro, Gwanak-gu, Seoul, Korea;
5University of Alberta, Edmonton, Alberta, T6G 2E9, Canada;
6Carleton University, 2115 Herzberg Laboratories, Ottawa, Ontario, K1S 5B6, Canada;
7North Carolina State University, 121 West Jones Street, Raleigh, North Carolina, 27601, USA;
8Institute of Paleontology of Mongolian Academy of Sciences, Chingeltei district-4, Sambuu Street, Ulaanbaatar-14201,
Hesperornithiforms have been predominantly reported from the marine Cretaceous deposits of the Western
Interior Seaway of North America, although sparse records of this group have also been reported from uvial
deposits in Asia and North America especially from the Maastrichtian. Because Asian hesperornithiform fossils
are extremely rare compared to North American specimens, the diversity of Asian taxa remains unclear. Here, we
report a complete right tibiotarsus (KID 310) of a hesperornithiform from the inner continental uvial deposits
of the Nemegt Formation (lower Maastrichtian) in the Gobi Desert of southwestern Mongolia, which was col-
lected in 2008 during the Korea-Mongolia International Dinosaur Expedition. e proximal tarsals (the astraga-
lus and the calcaneum) are completely fused to the distal epiphysis, indicating that it is an adult individual. It has
a bular crest extending to the mid-shaft and a laterally angled proximolateral articular surface. ese characters
are only seen in Hesperornithiformes. A shallow tibial incision further suggests the specimen can be assigned as
a non-hesperornithid hesperornithiform. Although the phylogenetic position of KID 310 within the clade of
Hesperornithiformes is ambiguous due to its preservation as an isolated bone, it presents unique morphological
characters such as the lateral margin of the cnemial crest being pointed and expanded laterally, and the bular
crest being remarkably expanded laterally. However, it is not clear if it is a new taxon because two other hes-
peornithiforms (Judinornis nogontsavensis and Brodavis mongoliensis) from the same formation do not preserve the
tibiotarsus. e body size of KID 310 is estimated to have been similar to that of Brodavis mongoliensis, which is
one of the smallest hesperornithiforms known. Inland hesperornithiforms in the Maastrichtian such as Judinornis
nogontsavensis, Brodavis mongoliensis, Brodavis americanus, and Brodavis baileyi have smaller body sizes in com-
parison to the contemporary taxa from marine deposits (e.g., Asiahesperornis sp. and Canadaga sp.), indicating
that hesperornithiform body sizes maybe related to their habitat environment (freshwater or marine).
Vertebrate Anatomy Morphology Palaeontology 9:139
A kinetic model of the palaeognath ribcage with
implications for understanding avian ventilation
Yan-yin Wang1 and Corwin Sullivan1,2
1Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada;;
2Philip J. Currie Dinosaur Museum, Wembley, AB, T0H 3S0, Canada,
In respiratory biology, ventilation is typically regarded as the process of transporting gas between the respira-
tory organ and the external environment. Scholars have acquired extensive knowledge of many aspects of ventila-
tion in archosaurs, including the anatomy of respiratory organs, the activity patterns of relevant muscles, and the
kinematics of the ribcage during ventilation. However, the kinetic forces and moments involved in ventilation
have been addressed in few studies, and most of these have been two-dimensional in scope and have focused on
only a portion of the thorax. A three-dimensional kinetic model can examine the thorax comprehensively and has
the potential to incorporate knowledge from other studies of respirations.
Here we present a kinetic model of the paleognathic ribcage to represent the condition of the ightless birds.
e skeletal elements were created by scanning the disarticulated thoracic bones of an ostrich using a FlexScan
3D surface scanner. e model was set up for analysis in Autodesk Maya and SIMM (Software for Interactive
Musculoskeletal Modelling). e kinematics of skeletal elements were described in terms of three kinematic rota-
tions (‘caliper’, ‘bucket handle’, and ‘pump handle’) around the relevant joint centres, whose positions and orien-
tations could only be estimated but were consistently positioned using anatomical landmarks in both Maya and
SIMM. e muscles of the left thorax were modelled as a total of 122 muscle vectors, based on dissection of an emu
and avian anatomical literature . Most hypaxial muscles have broad insertions on the ribs and cannot be accurately
represented as single vectors. Instead, individual muscles were modelled as multiple vectors spaced throughout the
area of insertion, with each vector representing a bundle of similarly oriented bres. Muscle properties used in the
model were based on data from human studies, as comparable information was not available for avians.
When a single skeletal element moves relative to the rest of the ribcage, the kinetic model indicates that some
muscles undergo substantial changes in moment arms which inuences the eciency of the muscles at rotating
the rib segments. Overall, muscle moment arms change according to non-linear curves (e.g., hyperbola, hyper-
bolic tangent) as joint rotation occurs. For a given vertebral rib, the moment arms of some muscles (e.g., Mm
intercostales externi) follow similar curves for all three kinematic rotations, but for other muscles (e.g., M levator
costarum) the three types of rotation cause moment arms to change in distinct ways. For a given M intercostalis
connecting two adjacent vertebral ribs, the moment arms change sign (and therefore the direction of the angular
acceleration) at dierent stages of rib rotation. e moment arm curves for some muscles suggest they may not
function exclusively in inspiration or in expiration, as previously indicated by experimental studies of Caiman
crocodilus and Gallus domesticus. However, the moment arm curves for Mm appendicocostales suggest these
muscle slips are solely inspiratory, which agrees with previous studies. Moment arm curves for Mm appendico-
costales resemble those for Mm intercostales externi, suggesting that Mm appendicocostales may have originated
as distinct slips of Mm intercostales externi like those present in crocodylians. Examinations of the muscle mo-
ment arms suggest that M. appendicocostalis in paleognathes inherited from their archosaur ancestors may have
originated to improve the eciency in avian ventilation in response to high metabolic demands.
Rening the current kinetic model should provide further insights into the drivers of ventilatory motions.
Furthermore, applying this modelling approach to other archosaurs may shed light on the evolution of ventila-
tion in this major amniote group.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
Taxonomy of a new goniopholidid specimen from the
Upper Jurassic Morrison Formation and their diversity
in North America
Junki Yoshida1, Atsushi Hori1, Yoshitsugu Kobayashi1, Michael J. Ryan2,
Yuji Takakuwa3, and Yoshikazu Hasegawa3
1Hokkaido University, Sapporo, Hokkaido, Japan;;
2Carleton University, Ottawa, Ontario, Canada;
3Gunma Museum of Natural History, Tomioka, Gunma Prefecture, Japan;; hasegawa@
Goniopholididae is a group of basal neosuchians found in the northern hemisphere during the Jurassic and
Early Cretaceous, and is closely related to the clade of Paralligatoridae and Eusuchia. Goniopholididae is the
earliest crocodyliform group to acquire the modern crocodylian body plan and an inferred semi-aquatic lifestyle.
Understanding the anatomy, phylogeny, and functional morphology of this group is important for revealing the
origin of the modern crocodylian body plan (e.g., platyrostrum and secondary palate) and lifestyle. Here we de-
scribe a well-preserved, nearly complete skeleton of a goniopholidid (GMNH-PV229), discovered from the sand-
stone of the Brushy Basin Member of the Upper Jurassic Morrison Formation at the East Camarasaurus Quarry,
Wyoming, USA, in 1993, and examine its phylogenetic relationships within the family.
Although most of the cranial and neurocentral sutures of the caudal vertebrae are fused, the cervical, dorsal,
and sacral vertebrae remain unfused, indicating the immaturity of the individual at death. e rostral skull length
(preorbital length) is 42 cm, one of the largest in goniopholidids, and 60% of the skull length, indicating a
medium long rostrum. e ratio of rostral width at the midpoint of the maxilla to the skull width is 0.64, while
other goniopholidids (e.g., A. stovalli) show a ratio of less than 0.5. e number of subfossae in the maxillary
depression is ve as in Goniopholis simus, while it is four in Amphicotylus lucasii and three in Goniopholis kiplingi
and Anteophthalmosuchus hooleyi. Posterior to the nasopharyngeal passage, the pterygoid has a small, shallow,
rectangular-shaped postchoanal fossa that is not perforated or connected to the passage and sinus.
Our data matrix for the phylogenetic analyses was composed of 486 characters and 102 ingroup and one out-
group (Gracilisuchus) taxa, including GMNH-PV229. A heuristic search was performed to obtain the most parsi-
monious trees using PAUP v. 4.0a. Our initial analysis produced 2592 most parsimonious trees with tree lengths
of 2400. Strict consensus trees in both analyses place GMNH-PV229 within Goniopholididae. A sister-taxa
relationship of GMNH-PV229 and Amphicotylus stovalli is supported by four synapomorphies: the anterior end
of the frontal is posterior to the prefrontal, the palatal shelves of the palatines do not fully contact at the mid-line,
the anterior border of the internal naris is positioned anterior to the suborbital fenestra, and the internal choana
is lanceolated. However, GMNH-PV229 diers from Amphicotylus stovalli in having a broad rostrum, a straight
lateral border of the nasals, a rounded anterior margin of the palatine, and lacking ‘Crest C’ on the ventral surface
of the quadrate. GMNH-PV229 has a unique combination of the following features: broad rostrum, ve subfos-
sae in the maxillary depression, anterior projection at the posterior margin of the naris, triangular palpebral, lack
of ‘Crest C’ on the quadrate, presence of postchoanal fossa, perichoanal fossa being wider than the nasophar-
yngeal passage, and the posterior border of the internal choana located at the midpoint of the pterygoid. ese
characters suggest that GMNH-PV229 is a new species of Amphicotylus.
Our results show a greater diversity of goniopholidids than previously known in the Upper Jurassic Morrison
Formation, which currently comprises Eutretauranosuchus, Amphicotylus stovalli, and A. lucasii, by adding the tax-
on represented by GMNH-PV229. GMNH-PV229 is characterized by its broad rostrum, suited for feeding on
Vertebrate Anatomy Morphology Palaeontology 9:139
large and agile prey, as in some derived Cretaceous goniopholidids such as Goniopholis simus, Goniopholis kiplingi,
and Anteophthalmosuchus hooleyi. We infer that a broad rostrum may have evolved much earlier than previously
suggested within goniopholidids for feeding on large, highly mobile animals in the freshwater environment.
How to make monsters: cladistic analysis of ontogeny
recovered evidence of anagenesis in North American
Amelia R. Zietlow
Richard Gilder Graduate School – American Museum of Natural History, 200 Central Park West, New York, NY 10024,
Mosasaurs were large, globally distributed aquatic lizards that lived during the Late Cretaceous. Despite num-
erous specimens of varying maturity, a detailed growth series has not been proposed for any mosasaur taxon.
Tylosaurus is a genus of particularly large mosasaurs with long, edentulous anterior extensions of the premaxilla
and dentary that lived in Europe and North America during the Late Cretaceous (90 to 66 million years ago).
ree taxa—Tylosaurus proriger, T. kansasensis, and T. nepaeolicus—have robust fossil records with specimens
spanning a wide range of sizes. Furthermore, because they lived in the same place and at the same time, and T.
kansasensis are generally smaller than T. nepaeolicus, previous work has hypothesized that they are a single taxon,
and T. kansasensis are juveniles. erefore, these species are ideal for testing hypotheses of ontogeny, synonymy (T.
kansasensis with T. nepaeolicus), sexual dimorphism, anagenesis, and heterochrony.
Fifty-nine hypothetical growth characters were identied, including size-dependent, size-independent, and
phylogenetic characters. Quantitative cladistic analysis was used to recover a growth series for each taxon: T.
proriger, 23 specimens and 17 growth stages (consistency index = 0.6, homoplasy index = 0.4); and T. nepaeolicus/
kansasensis, 19 specimens and 12 growth stages (consistency index = 0.6, homoplasy index = 0.4. e results
supported the synonymy of T. kansasensis with T. nepaeolicus and that T. kansasensis are juveniles of T. nepaeolicus.
A Spearman rank-order test resulted in a signicant (p < 0.05) correlation between size (skull length and quadrate
height) and maturity for both taxa, and evidence for skeletal sexual dimorphism was not found. Eleven growth
characters, including the development of a knob-like rostrum and increase in quadrate height relative to skull
length, were shared by both taxa.
Finally, a novel hypothesis of anagenesis (i.e., evolution within a single lineage) in Western Interior Seaway
Tylosaurus species, driven by peramorphy (extension of growth), was tested and supported by a third cladistic
analysis including specimens of both T. proriger (15 specimens) and T. nepaeolicus/kansasensis (13 specimens),
which recovered evidence of intermediate morphologies in both taxa and peramorphy of skull size and de-
velopment in T. proriger.
Canadian Society of Vertebrate Palaeontology 2021 Abstracts
Many thanks to CSVP 2021 virtual local organizing committee members:
Bassel Arnaout
Emily Bamforth
Julien Divay
Annie McIntosh
Hallie Street
Yan-yin Wang
Thanks also to the following people who served as abstract reviewers:
Hoai-Nam Bui
James Campbell
Nicola Howard
Sydney Mohr
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
Data from recent collections of Paleocene and Eocene mammals in the Western Interior of North America show marked inverse correlations both of generic diversity and relative abundance between multituberculates and rodents. The largest diminution in multituberculate diversity occurred in the latest Paleocene, near the Tiffanian-Clarkforkian boundary, not in the early Eocene as suggested previously. Reconstruction of diets, diel activity patterns, locomotor habits, and body sizes of multituberculates and rodents suggests that both groups potentially utilized similar resources. The hypothesis that competitive exclusion may have played a role in the decline of multituberculates is strengthened by recent evidence that rodents evolved in Asia, immigrating to North America in latest Pelocene time. Evidence in support of alternative hypothesis employed to account for the decline and eventual extinction of multituberculates is wanting.-from Author
Full-text available
In an effort to further our understanding of ecosystem structure on multiple temporal and biogeographic scales, the influence of competitive interactions in an invasive setting was explored in the fossil record. Using brachiopod morphology as a proxy for niche space occupation, the external shapes of three pairs of potentially competing brachiopod species were analyzed via three-dimensional baseline shape co-ordinates. Morphology of incumbents was compared before and after the Richmondian Invasion (Late Ordovician, Illinois Basin), and for each incumbent–invader pair: it was possible to differentiate the incumbents pre- and post-invasion; the incumbent became more morphologically different from the invader; and landmarks driving the morphological differences of two of the incumbents shift away from the invader in multidimensional morphospace. These results are consistent with character displacement, which supports the hypothesis that competition played a discernable role in the brachiopod community. This suggests that the use of morphometrics and morphospace occupation could provide a valuable tool for the exploration of ecological interactions in the geologic record, potentially providing novel interpretations of the effects of competition on community structure and evolution.
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More than 99 per cent of the roughly 58,000 living vertebrate species have jaws. This major clade, whose members are collectively known as gnathostomes ('jawed mouths'), made its earliest definitive appearance in the Silurian period, 444-416 million years (Myr) ago, with both the origin of the modern (crown-group) radiation and the presumptive invasion of land occurring by the end of the Devonian period (359 Myr ago). These events coincided with a major faunal shift that remains apparent today: the transition from Silurian ecosystems dominated by jawless fishes (agnathans) to younger assemblages composed almost exclusively of gnathostomes. This pattern has inspired several qualitative descriptions of the trophic radiation and ecological ascendance of the earliest jawed vertebrates. Here we present a quantitative analysis of functional variation in early gnathostome mandibular elements, placing constraints on our understanding of evolutionary patterns during this critical interval. We document an initial increase in functional disparity in the Silurian that stabilized by the first stage of the Devonian, before the occurrence of an Emsian (∼400 Myr ago) oxygenation event implicated in the trophic radiation of vertebrates. Subsequent taxonomic diversification during the Devonian did not result in increased functional variation; instead, new taxa revisited and elaborated on established mandibular designs. Devonian functional space is dominated by lobe-finned fishes and 'placoderms'; high disparity within the latter implies considerable trophic innovation among jaw-bearing stem gnathostomes. By contrast, the major groups of living vertebrates--ray-finned fishes and tetrapods--show surprisingly conservative mandibular morphologies with little indication of functional diversification or innovation. Devonian gnathostomes reached a point where they ceased to accrue further mandibular functional disparity before becoming taxonomic dominants relative to 'ostracoderm'-grade jawless fishes, providing a new perspective on classic adaptive hypotheses concerning this fundamental shift in vertebrate biodiversity.
Aim To test for community-wide character displacement in New Zealand skinks. Location Four small islands in the New Zealand archipelago. Methods (1) We conducted a field experiment on a single island to evaluate whether prey size selection is correlated with lizard body size. We pitfall trapped 69 skinks from three species, measured several aspects of their morphology and presented each animal with a variety of different-sized prey in a food choice experiment. (2) We tested whether the morphological characteristics associated with prey size selection were evenly partitioned in four island skink communities using null models. Results Prey size selection was associated with skink morphology; larger skinks consumed larger prey. Null model analyses showed support for evenly displaced body sizes on one island, weak support on one island and no support on two islands. Main conclusions Results showed mixed support for community-wide character displacement in New Zealand skinks. Differences in body sizes appear to reflect the use of different-sized prey. Even differentiation in body sizes on one island suggests that species coexistence is facilitated by interspecific differences in prey size selection. However, little support was found on other islands, suggesting that other factors, such as interspecific differences in habitat selection and/or diurnal activity patterns, may interact with differences in prey size selection to promote coexistence among New Zealand skinks.
Ecological character displacement occurs when sympatric species compete with one another, resulting in morphological divergence. Theoretically, character displace-ment can evolve from a number of ecological interactions, such as exploitation, interference, or predation, but most examples describe species competing exploitatively for limiting resources (typically food). Here I report a case of character displacement evolving from aggressive behavioral interference, found in a well-studied system of terrestrial salamanders of the genus Plethodon. Using geometric morphometrics, I found parallel shifts in head shape from allopatry to sympatry in both P. jordani and P. teyahalee, and found significantly greater morphological divergence in sympatry relative to allopatry. Both findings are con-sistent with ecological character displacement. I also show a significant association between morphology and aggressive behavior, demonstrating a direct link between interference competition and morphology. I present a modified set of the criteria for character displace-ment that are appropriate for discriminating character displacement via aggressive inter-ference from other possible evolutionary mechanisms. For this example, empirical support satisfying five of the six criteria for character displacement is found. These results provide evidence that morphological variation can be generated by mechanisms other than resource exploitation, which has profound implications for interpreting patterns of biological di-versity.