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A king-size theropod coprolite


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Fossil faeces (coprolites) provide unique trophic perspectives on ancient ecosystems. Yet, although thousands of coprolites have been discovered, specimens that can be unequivocally attributed to carnivorous dinosaurs are almost unknown. A few fossil faeces have been ascribed to herbivorous dinosaurs, but it is more difficult to identify coprolites produced by theropods because other carnivorous taxa coexisted with dinosaurs and most faeces are taxonomically ambiguous. Thus sizeable (up to 20 cm long and 10 cm wide) phosphatic coprolites from Belgium and India that have been attributed to dinosaurs might have been produced by contemporaneous crocodylians or fish. But there is no ambiguity about the theropod origin of the Cretaceous coprolite we report here. This specimen is more than twice as large as any previously reported carnivore coprolite, and its great size and temporal and geographic context indicate that it was produced by a tyrannosaur, most likely Tyrannosaurus rex. The specimen contains a high proportion (30-50%) of bone fragments, an it rare tangible evidence of theropod diet and digestive processes.
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Nature © Macmillan Publishers Ltd 1998
A king-sized theropod
Karen Chin, Timothy T. Tokaryk*, Gregory M. Erickson
& Lewis C. Calk
United States Geological Survey, 345 Middlefield Road, MS 975, Menlo Park,
California 94025, USA
* Eastend Fossil Research Station, Royal Saskatchewan Museum, Box 460,
Eastend, Saskatchewan S0N 0T0, Canada
Department of Integrative Biology & Museums of Vertebrate Zoology and
Paleontology, University of California, Berkeley, California 94720, USA
Fossil faeces (coprolites) provide unique trophic perspectives on
ancient ecosystems. Yet, although thousands of coprolites have
been discovered, specimens that can be unequivocally attributed
to carnivorous dinosaurs are almost unknown. A few fossil faeces
have been ascribed to herbivorous dinosaurs
, but it is more
difficult to identify coprolites produced by theropods because
other carnivorous taxa coexisted with dinosaurs and most faeces
are taxonomically ambiguous. Thus sizeable (up to 20 cm long
and 10 cm wide) phosphatic coprolites from Belgium
and India
that have been attributed to dinosaurs might have been produced
by contemporaneous crocodylians
or fish. But there is no ambiguity
about the theropod origin of the Cretaceous coprolite we report
here. This specimen is more than twice as large as any previously
reported carnivore coprolite, and its great size and temporal and
geographic context indicate that it was produced by a tyrannosaur,
most likely Tyrannosaurus rex. The specimen contains a high
proportion (3050%) of bone fragments, and is rare tangible
evidence of theropod diet and digestive processes.
The specimen (SMNH P2609.1) was discovered as an elongate
mass weathering out of the fluvial Maastrichtian Frenchman For-
mation in Southwestern Saskatchewan, roughly 35 km southeast of
the town of Eastend. The fractured mass was distinguished by its
indurated nature and numerous inclusions of comminuted bone.
The main portion of the mass was found in situ in a bentonitic
mudstone, though numerous fragments had eroded downslope. No
fossil bones were found in association with the coprolite, but fossils
of a number of large vertebrates have been recovered from the
Frenchman Formation
The main body of the specimen is roughly 44 cm long, 13 cm high
and 16 cm wide (Fig. 1). The density of the material (approximately
2.94 g ml
) and the weight of all portions (over 7.1 kg) indicate that
the present volume of the mass is ,2.4 litres, though it is likely that
the original faecal mass was larger before it was subjected to
compaction, attrition, and/or desiccation. Broken surfaces of the
specimen expose numerous dark brown macroscopic bone frag-
ments ranging from 2 to 34 mm in length. These pieces are
suspended in a microcrystalline ground mass and are generally
aligned in a consistent direction. The ground mass also contains
sand-sized bone clasts (Fig. 2). Most of the included bone appears to
be similar in type, with highly vascularized cortical bone tissue up to
14-mm thick in a fibrolamellar pattern. All of the observed bone is
primary, and no lines of arrested growth were detected.
Bulk chemical analyses using X-ray fluorescence (Table 1) reveal
marked differences between the specimen and the Frenchman
Formation mudstone. The bone-bearing specimen contains high
concentrations of phosphorus and calcium, and lower concentra-
tions of aluminium and silicon, relative to the host sediment.
Microprobe analyses of specific areas of the specimen indicate
that the bone fragments and coprolitic ground mass have similar
compositions, though the ground mass contains more silicon and
aluminium (Table 2). X-ray powder-diffraction analyses indicate
that carbonate fluorapatite is the predominant phosphate mineral
in both the bone and the ground mass.
Several factors confirm that this specimen is a coprolite. The most
diagnostic feature is a phosphatic composition, which is character-
istic of carnivore coprolites
. As phosphorus normally constitutes
only about 0.1% of the Earths crustal rocks
, concentrated phos-
phate deposits usually indicate biotic accumulations, and the overall
configuration of the mass is consistent with the irregular faecal
deposits produced by very large animals. The matrix-supported
distribution of bone fragments argues against the possibility that the
mass represents regurgitated material or fluvially aggregated bone
The tremendous size of the specimen indicates that the faecal
mass was produced by a large theropod. The largest theropod found
in the Frenchman Formation is Tyrannosaurus, with an estimated
body weight of 5,400 to 6,300 kg (ref. 11). Although other ther-
opods, crocodylomorphs, and a chelonian (Dromaeosaurus,
Saurornitholestes, Troodon, Richardoestesia, Chirostenotes,an
ornithomimid, Leidyosuchus, Champsosaurus, and Aspideretes)
have also been recovered from the Frenchman Formation
, these
smaller carnivorous taxa probably weighed ,100 kg (ref. 12), and it
letters to nature
VOL 393
18 JUNE 1998
Present address: Biomechanical Engineering Division, Mechanical Engineering Department & Reha-
bilitation R & D Center, VA Health Care System, Stanford University, Stanford, California 94305, USA.
Figure 1 Large, bone-bearing theropod coprolite with some of the broken pieces
that had eroded downslope. This specimen was found in Chamberry Coulee in
the Frenchman River Valley, roughly 11.5 m below the Cretaceous/Tertiary
boundary. Scale bar,10 cm.
Figure 2 Photomicrograph of a thin section of the theropod coprolite, showing
sand- to pebble-sized bone clasts within a microcrystalline phosphatic ground
mass. The elemental composition of the ground mass is similar to that of the bone
fragments, indicating that it is probably largely composed of reprecipitated bone
apatite infiltrated by clay minerals from the host sediment (Table 1). The large
bone fragment in the upper left portion of the image exhibits a fibrolamellar
pattern, with osteocyte lacunae concentrically arranged around the vascular
canals. Probe measurements of the interior of bone lacunae revealed that many
of these channels are at least partially empty, whereas others exhibit variable
element distributions, with generally lower concentrations of calcium and
phosphorus, and higher silicon and aluminium levels (Table 2). Scale bar, 400 mm.
Nature © Macmillan Publishers Ltd 1998
is unlikely that they could have produced large quantities of faeces.
The mass could have been produced by a different species of
tyrannosaur, but no others have been recognized in the Frenchman
The stomach acids and proteolytic enzymes of large extant
carnivores digest bone to varying degrees
. Tangible evidence
of this process is apparent in areas of the theropod coprolite where
aligned and rounded bone pieces represent the degraded remains of
large bone fragments (Fig. 3). The contents of carnivore coprolites
might reflect animal physiology, because the extent of bone diges-
tion can be indicative of gut-residence time
. Carnivore feeding
activity is usually variable, however, and stomach acidity and gut-
residence time can be altered by non-physiological factors such as
frequency of meals
. Even so, the high percentage of incompletely
digested bone in this specimen is interesting because it is incon-
sistent with the general prediction that large theropods digested
most consumed bone
in the manner of extant crocodilians
The chemistry of the coprolite reflects several factors. A large
percentage of the phosphate of the ground mass was probably
derived from dissolved bone apatite, but other dietary residues
would have contributed additional phosphorus, as microorganisms
and animal soft tissues contain significant concentrations of this
element. Postdepositional phosphate precipitation may have been
triggered by bacterial enzymes
after burial of the faecal mass.
Although the chemistry of this diagenetic phosphate is similar to
that of the included bone, the increased amounts of silicon and
aluminium and small differences in amounts of other elements
indicate contributions from the host sediment. Thus, although the
overall phosphatic composition of the coprolite reflects a carnivor-
ous diet, minor chemical differences in the bone and ground mass
seem to reveal more about diagenesis than about diet.
Histological and morphological analyses of the included bone
fragments give clues to the identity of the ingested animal. Dino-
saurs are the only Late Cretaceous animals that regularly produced
thick fibrolamellar cortical bone
. The absence of secondary
osteons indicates that the bone was ontogenetically juvenile, so
the ingested animal appears to have been a subadult dinosaur.
Although bone histology is not species-specific, the absence of
arrested growth lines may indicate an ornithischian dinosaur.
Lines of arrested growth have been observed in several theropods
but have not been observed in the long bones of Triceratops and
Edmontosaurus (G.M.E., unpublished observation), the most
common dinosaurs found in the Frenchman Formation. Other
ornithischians from the formation include Torosaurus,
Thescelosaurus and an ankylosaur
The thickness of the cortical bone indicates that the fragments
may be derived from appendicular bone or ceratopsian frill. If the
fragments were derived from long-bone diaphyses, estimates of the
of the consumed animal might range from , 200 kg (for a
bipedal dinosaur) to 750 kg (for a quadrupedal dinosaur). The
pronounced fragmentation and angularity of the consumed bone
indicate that it was fractured before ingestionapparently by biting
during feeding. Although extant birds (avian dinosaurs) often use a
horny gizzard and/or ingested grit for food maceration
, such
mechanisms could not have been solely responsible for the degree
of comminution seen in the coprolite. Furthermore, significant
trituration would have resulted in well rounded bone clasts, and
there is no evidence for the use of gastroliths by non-avian
The coprolitic evidence for extensive bite-induced bone frag-
mentation is surprising in view of modern reptilian feeding habits.
Extant reptiles have poor dental occlusion and generally swallow
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Table 1 X-ray-fluorescence data of the weight percentage of oxides found in
bulk powdered samples of the coprolite and host sediment
Coprolite Host sediment
7.93 70.2
2.43 18.1
0.128 0.794
FeO 0.95 6.02
MnO 0.151 0.018
CaO 44.6 0.97
MgO 0.16 1.42
O 0.27 2.22
0.28 1.08
26.5 0.70
Total 83.5 100.9
The clay-rich sediment reflects the low phosphorus concentration of most inorganic rocks,
whereas the coprolite is largely composed of biotically concentrated phosphorus and
Figure 3 Photomicrograph of a thin section of the theropod coprolite, showing
associated bone fragments that indicate digestive degradation. Digestive acids
and enzymes probably infiltrated the interior of the bone through vascular canals.
Scale bar,100 mm.
Table 2 Microprobe data indicating weight percentage of oxides, fluorine and chlorine in different regions of the coprolite
Bone fragments
n ¼ 60 points
Ground mass
n ¼ 60 points
Bone lacunae
n ¼ 27 points
Mean s.d. Mean s.d. Mean s.d.
0.038 0.102 4.03 1.42 29.5 13.2
0.094 0.046 1.71 0.516 13.6 5.80
FeO 0.484 0.034 0.730 0.101 3.24 1.39
MnO 0.230 0.026 0.144 0.018 0.068 0.046
MgO 0.103 0.018 0.210 0.030 1.02 0.47
CaO 51.5 0.290 48.9 1.09 20.2 13.5
SrO 0.157 0.030 0.117 0.024 0.036 0.040
O 0.335 0.046 0.237 0.032 0.184 0.056
O 0.025 0.010 0.163 0.044 0.312 0.110
0.142 0.055 0.285 0.029 0.157 0.080
35.7 0.466 32.6 0.859 13.4 9.37
F 2.95 0.074 2.62 0.117 0.943 0.750
Cl NA NA 0.108 0.090
Total 90.5 0.582 90.7 0.584 82.4 4.96
The compositions of the bone and ground mass are similar, though the ground mass appears to contain more contributions from the host sediment. Of 67 probe measurements of lacunae,
40 registered low element totals, indicating that the vascular canals were incompletely filled. These channels would have acted as conduits for digestive fluids and for postdepositional
contaminants. Data listed above are from the 27 lacunae that registered element totals over 70%. NA, no analyses done.
Nature © Macmillan Publishers Ltd 1998
large pieces of prey whole
. Such observations of modern feeding
behaviours have led to speculation that extinct theropods did little
and wasted a significant proportion of the food
available from carcasses
. Tyrannosaur teeth appear to be stout
enough to damage bone
, however, and analyses of bite marks on
Triceratops and Edmontosaurus bones indicate that Tyrannosaurus
pulverized bones during feeding
and probably consumed bone
Although a single coprolite cannot be construed as representative
of diet, this rare example of fossilized dietary residues helps to refine
our understanding of theropod feeding behaviour by providing
physical evidence that a tyrannosaur crushed, consumed, and
incompletely digested large quantities of bone when feeding on a
subadult dinosaur. It also presents a new search image for future
discoveries of theropod faeces that will help us to elucidate the food
habits of these giant meat-eaters.
. ... . . . . .. . . . ... . . . . .. . . . ... . . . . .. . . . ... . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . .
Bulk chemical analyses of the coprolite and host sediment (Table 1) were made
on a Rigaku 3370 spectrometer by the staff of the GeoAnalytical Laboratories,
Washington State University, using described procedures
Mineralogical compositions of the bone and ground mass were examined
with a Phillips V2.0 diffractometer at the University of California, Santa
Barbara (scanning from 2808 v). Elemental analyses of these components
(Table 2) were made on a JEOL 8900 microprobe at the US Geological Survey,
Menlo Park. A 15 kV, 20 nA beam defocused to produce a spot size of 15 mm
was used to analyse bone and ground mass; a 10 nA current was used for
lacunae analyses. Natural minerals (Wilberforce apatite, Tiburon albite,
strontianite, barite, San Carlos olivine, and sodalite) and synthetic materials
(faylite, Mn
, An100, and GSC glass) were used as standards.
Received 22 January; accepted 23 March 1998.
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permitting access to the land and its fossils; H. N. Bryant, M. J. Jurashius, C. E. Meyer, M. Moreno, R. L.
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Correspondence and requests for materials should be addressed to K.C. (e-mail: kchin@pangea.stanford.
letters to nature
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Genetics underlying
inbreeding depression
in Mimulus with
contrasting mating systems
Michele R. Dudash & David E. Carr*
Department of Biology, University of Maryland, College Park, Maryland 20742,
* Blandy Experimental Farm, University of Virginia, Route 2, Box 210, Boyce,
Virginia 22602, USA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The importance of inbreeding depression in theoretical consid-
erations of mating-system evolution
and its potential impact on
the persistence of small populations
has renewed interest in the
genetic basis of this phenomenon. Inbreeding increases homo-
zygosity. This can produce inbreeding depression for two differ-
ent reasons: first, deleterious recessive or partially recessive alleles
that are masked at heterozygous loci by dominant alleles become
fully expressed in homozygotes; and second, alleles may interact
in an overdominant manner, such that the fitness of either type of
homozygote is lower than that of heterozygotes. These two
mechanisms produce different long-term effects in populations
experiencing increased levels of inbreeding. Inbreeding depres-
sion resulting from deleterious alleles can be removed by selec-
tion, but inbreeding depression produced by overdominance
cannot be removed without lowering the mean fitness of the
. Using a North Carolina 3 breeding programme
the most powerful quantitative genetics technique available
we show here that deleterious recessive alleles are mainly respon-
sible for inbreeding depression in two closely related annual
plants, the primarily selfing Mimulus micranthus and the
mixed-mating M. guttatus. Estimates indicate that deleterious
alleles in M. micranthus are more nearly additive than they are in
M. guttatus.
The genetic basis of inbreeding depression (or its converse,
heterosis) has been examined primarily in crop plants. There
is evidence for both dominance-based
and overdominance-
inbreeding depression. However, the relative impor-
tance of dominance-based versus overdominance-based inbreed-
ing depression in natural plant populations is largely unknown.
Studies of Eichhornia paniculata
(Pontederiaceae) and two
Amsinckia species
(Boraginaceae) have found indirect evidence
for dominance-based inbreeding depression.
The genus Mimulus (Scrophulariaceae) has been the focus of many
studies aimed at understanding the processes responsible for the
evolution of plant mating systems
. Mimulus guttatus, the common
monkey flower, has large, bee-pollinated flowers, and measured
outcrossing rates for three populations, including one used in this
study, ranged from 0.680.80 (ref. 25). Mimulus micranthus is a
... Coprolites (fossilised faeces) always possess partially digested or undigested food remains, which provide a valuable palaeobiological source for interpreting the diet (herbivore, carnivore, or omnivore), feeding behaviours, and digestive physiology of the host animals (e.g. Chin et al., 1998;Prasad et al., 2005;Hunt et al., 2007;Eriksson et al., 2011;Zatoń and Rakociński, 2014;Zatoń et al., 2015). Thus, coprolites may reveal predator-prey interactions among animals, allowing for the reconstruction of the diversity and trophic structure of ancient ecosystems (e.g. ...
... The presence of undigested fish remains suggests that complete food digestion did not occur among the sharks of the Ordos Basin. Moreover, the survival of cancellous bones indicates that the digestive efficiency of Middle Triassic hybodonts was possibly inferior to that of extant sharks, and similar digestive differences between fossil and extant species are also known in archosauromorphs (Chin et al., 1998) and crocodilians (Milàn, 2012). The Fig. 7. Photos and inclusions of the morphotype F coprolites (non-spiral ones with an elongate shape). ...
The early Ladinian lacustrine ecosystem of the Chang 7 Member in the Ordos Basin was proposed as the earliest known Mesozoic-type, trophically multileveled lacustrine ecosystem after the end-Permian mass extinction (EPME). However, limited evidence of higher-order trophic levels represented by predatory fish has made this conclusion elusive. In this study, we investigated the external morphology, food inclusions, and geochemical composition of 54 vertebrate coprolites from organic-rich lacustrine sediments of Chang 7 Member, Yanchang Formation, in the Bawangzhuang section, Tongchuan City, Shaanxi Province, China. These coprolites were identified as seven morphotypes in three groups: three heteropolar spiral forms, two amphipolar spiral forms, and two non-spiral forms. Preserved inclusions (fish scales, bone fragments, teeth) indicated that the producers of these coprolites were piscivorous animals. Compared with coprolites previously researched, all coprolites described herein were inferred to be produced by fish: three heteropolar types of spiral coprolites derived from three types of hybodonts, two amphipolar spiral coprolites from coelacanth or Saurichthys with simple spiral valves, and non-spiral coprolites from at least two predatory actinopterygians. Thus, the biodiversity of the lacustrine paleoecosystem, particularly that of predators with upper trophic levels, was substantially enriched. The existence of large carnivorous predators of different taxa as apex predators in a trophically multileveled (at least six levels) lacustrine ecosystem indicates that the early Ladinian lacustrine ecosystem of the Ordos Basin marks the rebuilding of the top-predator trophic structure in the lacustrine ecosystem after the EPME.
... Conservatism in non-avian theropod gastrointestinal organization. The reconstruction of the gastrointestinal track in extinct taxa, including dinosaurs, could be inferred, indirectly, from gut content remains; less frequently by the analysis of coprolite contents; and rarely from exceptionally preserved remnants of the soft tissues [37][38][39][40][41][42][43][44][45][46][47][48] . The topographic distribution of the bluish layer in the caudal half of the ribcage in IMMNH-PV00731 (Fig. 1, Supplementary Information) Methods UV fluorescence photography. ...
Full-text available
Dromaeosaurids were bird-like dinosaurs with a predatory ecology known to forage on fish, mammals and other dinosaurs. We describe Daurlong wangi gen. et sp. nov., a dromaeosaurid from the Lower Cretaceous Jehol Biota of Inner Mongolia, China. Exceptional preservation in this specimen includes a large bluish layer in the abdomen which represents one of the few occurrences of intestinal remnants among non-avian dinosaurs. Phylogenetically, Daurlong nests among a lineage of short-armed Jehol Biota species closer to eudromaeosaurs than microraptorines. The topographic correspondence between the exceptionally preserved intestine in the more stem-ward Scipionyx and the remnants in the more birdlike Daurlong provides a phylogenetic framework for inferring intestine tract extent in other theropods lacking fossilized visceral tissues. Gastrointestinal organization results conservative among faunivorous dinosaurs, with the evolution of a bird-like alimentary canal restricted to avialan theropods.
... Phosphatic preservation is a characteristic component of carnivore coprolites, e.g., [1,4,59]. It has been suggested that rapid precipitation (within weeks-e.g., [14,19,60]) of dietary calcium phosphate can result in the preservation of fine morphological information [4,61]. ...
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The reconstruction of ancient trophic networks is pivotal to our understanding of ecosystem function and change through time. However, inferring dietary relationships in enigmatic ecosystems dominated by organisms without modern analogues, such as the Carboniferous Mazon Creek fauna, has previously been considered challenging: preserved coprolites often do not retain sufficient morphology to identify the dietary composition. Here, we analysed n = 3 Mazon Creek coprolites in concretions for dietary signals in preserved biomarkers, stable carbon isotope data, and macromolecular composition. Cholesteroids, metazoan markers of cholesterol, show an increased abundance in the sampled coprolites (86 to 99% of the total steranes) compared to the surrounding sediment, indicating an endogenous nature of preserved organics. Presence of unaltered 5α-cholestan-3β-ol and coprostanol underline the exceptional molecular preservation of the coprolites, and reveal a carnivorous diet for the coprolite producer. Statistical analyses of in situ Raman spectra targeting coprolite carbonaceous remains support a metazoan affinity of the digested fossil remains, and suggest a high trophic level for the coprolite producer. These currently oldest, intact dietary stanols, combined with exquisitely preserved macromolecular biosignatures in Carboniferous fossils offer a novel source of trophic information. Molecular and biosignature preservation is facilitated by rapid sedimentary encapsulation of the coprolites within days to months after egestion.
... Este investigador determinó que los excrementos de hiena manchada presentaban un porcentaje de Ca de 25.54% ± 10.72%, por lo que los resultados de nuestra muestra quedan dentro del intervalo de confianza dado por Kruuk (1972). Respecto a la concentración de fosfatos (P), su peso es esperable debido al origen biótico de los coprolitos, ya que el contenido normal de fósforo en los cristales de roca es de 0.1% (Chin et al. 1998). La presencia de otros elementos como Al o Si se debería a la incorporación de estos elementos propios del sedimento en el que los restos fueron depositados (Larkin et al. 2000). ...
... This fascination extends to many professional paleontologists. The great beast has been the focus of an outsized number of modern studies on its size, growth, locomotor performance, population dynamics, soft tissue preservation, and predatory capabilities (Paul, 1988(Paul, , 2008Carpenter, 1990;Molnar, 1991Molnar, , 2008Horner, 1994;Chin et al., 1998;Carpenter & Smith, 2001;Carrano & Hutchinson, 2002;Brochu, 2003;Carr & Williamson, 2004;Erickson et al., 2004;Sampson & Loewen, 2005;Schweitzer et al., 2007;Schweitzer et al., 2016;Happ, 2008;Holtz, 2008;Hutchinson et al., 2011;Currie 2011, 2016;DePalma et al., 2013;Myhrvold, 2013;Wick, 2014;Gignac & Erickson, 2017;Cost et al., 2019;Persons et al., 2019;Snively et al., 2019;Carr, 2020;Woodward et al., 2020;Bijiert et al., 2021;Marshall et al., 2021;Ullmann et al., 2021). In 2008, an entire multi-author technical book (Larson and Carpenter 2008) was dedicated to the one paleospecies T. rex, a rare event in the dinosaur literature. ...
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All skeletal specimens of the North American dinosaur Tyrannosaurus and a number of trace fossils have been attributed to the single species: T. rex. Although an unusual degree of variation in skeletal robustness among specimens and variability in anterior dentary tooth form have been noted, the possibility of sibling species within the genus Tyrannosaurus has never been tested in depth in both anatomical and stratigraphic terms. New analysis, based on a dataset of over three dozen specimens, finds that Tyrannosaurus specimens exhibit such a remarkable degree of proportional variations, distributed at different stratigraphic levels, that the pattern favors multiple species at least partly separated by time; ontogenetic and sexual causes being less consistent with the data. Variation in dentary incisiform counts correlate with skeletal robusticity and also appear to change over time. Based on the current evidence, three morphotypes are demonstrated, and two additional species of Tyrannosaurus are diagnosed and named. One robust species with two small incisors in each dentary appears to have been present initially, followed by two contemporaneous species (one robust and another gracile) both of which had one small incisor in each dentary, suggesting both anagenesis and cladogenesis occurred. The geological/geographic forces underlying the evolution of multiple Tyrannosaurus species are examined. A discussion of the issues involving the recognition and designation of multiple morphotypes/species within dinosaur genera is included.
... The largest derived tyrannosaurids such as Tyrannosaurus and Tarbosaurus used their tremendous bite strength and robust dentition (Erickson et al., 1996;Gignac and Erickson, 2017) to eat large prey such as ceratopsians and hadrosauroids (e.g., DePalma et al., 2013), and to break and swallow chunks of bone while doing so (Chin et al., 1998). This so-called 'puncture-pull' feeding would have given these species, or at least the most mature individuals among them, access to larger prey and a nutrition source (bone itself) that smaller and weakerbiting theropods could not exploit. ...
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Tyrannosaurid theropods topped the terrestrial food chain in North America and Asia during the latest Cretaceous. Most tyrannosaurids, exemplified by Tyrannosaurus rex, had deep snouts, thick teeth, and large jaw muscles that could generate high bite forces. They coexisted in Asia with a morphologically divergent group of long-snouted relatives, called alioramins. Qianzhousaurus sinensis, from the Maastrichtian of Ganzhou, China, is the largest alioramin yet discovered, but has only been briefly described. Here we present a detailed osteological description of the holotype cranium and mandible of Qianzhousaurus. We identify several new autapomorphic features of the genus, and new synapomorphies that unite alioramins (Qianzhousaurus, Alioramus altai, Alioramus remotus) as a clade, including a laterally projecting rugosity on the jugal. We clarify that the elongate skull of alioramins involves lengthening of the anterior palate but not the premaxilla, and is reflected by lengthening of the posterior bones of the lower jaw, even though the posterior cranium (orbit and lateral temporal fenestra) are proportionally similar to deep-skulled tyrannosaurids. We show that much of the variation among the alioramin species is consistent with growth trends in other tyrannosaurids, and that A. altai, A. remotus, and Qianzhousaurus represent different ontogenetic stages of progressive maturity, across which the signature nasal rugosites of alioramins became less prominent. We predict that the holotype skull of Qianzhousaurus represents the adult level of maturity for alioramins, and propose that the skull morphology of Qianzhousaurus indicates a much weaker bite than deep-skulled tyrannosaurids, suggestive of differences in prey choice and feeding style.
Postcranial remains of a small teleosauroid from the Upper Jurassic of north-eastern Italy are described in detail. The specimen, discovered in 1980 on a slab of Rosso Ammonitico Veronese (RAV Fm.; Bajocian–Tithonian), is represented by partially articulated thoracic, sacral and anterior caudal vertebrae, fractured and displaced osteoderms and pelvic girdle elements. Additional bone elements overlap one another in a densely packed cluster. The peculiar arrangement of this specimen is here interpreted as the result of regurgitation of the animal carcass from a pelagic predator or scavenger. Microstructural and geochemical evidence from bone and surrounding matrix support this hypothesis. A dearth of phosphorus in the matrix near the bone mass corroborates the interpretation of the specimen as a regurgitalite rather than a coprolite. Calcareous nannofossil and stratigraphic data allow us to assign the fossil to the latest Kimmeridgian or earliest Tithonian. The specimen is here tentatively referred to the teleosauroid subfamily Aeolodontinae based on the alternating pattern of the osteoderm ornamentation; this attribution is supported by stratigraphical and palaeoenvironmental evidence. If confirmed, this represents the first occurrence of Aeolodontinae in Italian outcrops of the western Tethys margin and represents the first marine crocodylomorph described as a bromalite.
In studying the skeletal allometry of any vertebrate, it is important to sample the ontogenetic extremes to ensure the accuracy of parameter estimation; this is particularly true for fossil taxa, where sampling of ontogenetic series is incomplete and sporadic. Previous studies have examined allometry in the skull of the duck-billed dinosaur Gryposaurus notabilis, but these did not include individuals smaller than ~65% the maximum known size (based on linear dimensions). Here, we report on the two smallest known examples of this species (a mostly complete skeleton and a partial skull), which are ~37% the known maximal size of G. notabilis. Osteohistology indicates that these represent individuals ~2 years of age. Allometric analysis demonstrates that most aspects of the skull of G. notabilis grew isometrically, although the height of the nasal arch grew with positive allometry. Early in the ontogeny of G. notabilis, the dentary teeth possessed secondary ridges, which were lost later in life. This finding has important bearing on hadrosaurid tooth taxonomy. The limb proportions of G. notabilis largely grew isometrically (or with weak negative allometry, at most), like some other hadrosaurids, suggesting that the species did not undergo a gait shift with increasing age (unless it occurred very early in ontogeny). We argue that the lack of significant locomotory performance compensation exhibited by young hadrosaurids helps to explain why they apparently formed small, mutualistic aggregations, presumably for protection from large predators.
Carnivores make traces on bones with their teeth when feeding. A true predatory bite trace (predichnia) forms when a predator catches and kills its prey or attempts to do so. Both predators and scavengers may leave their nonpredatory feeding traces during postmortem food processing. Despite the interpretative uncertainties as to the ethology such ichnofossils may represent, the bite traces have been traditionally classified as predichnia—traces of predation. Previously, there was no alternative ethological category available for workers to classify them. The present paper fills that gap and describes tooth-made ichnofossils from the continental Upper Triassic Grabowa Formation of southern Poland. It discusses modes the serration and striations might have formed along Linichnus edges, potential makers of the trace fossils, feeding strategies, and food-processing behaviors the ichnites may represent. All the bite traces are thought to act as a record of carnivorous behaviors and are classified as sarcophagichnia, a new ethological category (traces of feeding on a body). Finally, all the studied bite traces were likely inflicted postmortem and are classified as necrophagichnia (traces of feeding on an already dead body), most likely produced by scavengers in the studied cases. Data on recent carnivores link these ichnites with postmortem food-processing behaviors, such as dismembering and defleshing. Scavenging could, in fact, have been a preferred carnivorous feeding strategy in the seasonal Norian climate of the area. Dry seasons could have perhaps increased vertebrate mortality rates and provided plenty of carcasses for carnivores to feed on.
Our understanding of the early evolution of birds has advanced over the past 2 decades, thanks to an ever-improving fossil record. Extraordinary fossils have revealed new details about the evolution of the avian brain, respiratory system, digestive tract, and reproductive system. Many of the traits most strongly associated with birds first arose in nonavian theropod dinosaurs. Theropods evolved pennaceous feathers, incipient wings, and gliding flight long before modern birds appeared. Birds likewise inherited features such as an expanded forebrain, gizzard, dorsally immobile lung, pigmented eggs, and paternal brooding system from their theropod ancestors. Yet, the earliest birds also retained primitive traits such as teeth, clawed hands, long bony tails, partially buried nests, and slower growth. The evolution of birds was profoundly influence by the Cretaceous–Paleogene mass extinction, which wiped out the previously dominant Enantiornithines (“opposite birds”). This sets the stage for modern birds to radiate into the most diverse major clade of tetrapods.
It has been suggested that certain fossil assemblages consisting of disarticulated and broken remains of small to medium-sized vertebrates (“microvertebrate concentrations”) may be accumulations of incompletely digested material defecated by crocodilians. Experiments on crocodilian digestion show, however, that these reptiles demineralize calcified tissues, frequently leaving intact organic matrices of dentine, cementum, and bones in their feces. Such matrices, even if preserved as fossils, would not resemble most specimens in microvertebrate concentrations. Therefore, crocodilian digestion does not appear to have been an important factor in the formation of these fossil assemblages. Teeth similar to those defecated by crocodilians nevertheless do occur in the fossil record. Such teeth, lacking enamel but often complete in other respects, are interpreted here as having been digested by crocodilians, defecated as demineralized organic matrices, and subsequently remineralized. Enamel, with its extremely low organic content, does not yield a demineralized matrix susceptible to remineralization. A number of recently recognized occurrences of enamel-less teeth attest to the significance of crocodilian digestion as a factor in the taphonomic history of many Mesozoic and Cenozoic fossil vertebrate assemblages.