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Re-description of 'Steneosaurus' obtusidens Andrews, 1909, an unusual macrophagous teleosaurid crocodylomorph from the Middle Jurassic of England

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Teleosaurids were a clade of crocodylomorphs that attained near-global distribution during the Jurassic Period. Within Teleosauridae, one particular sub-clade of durophagous/macrophagous taxa achieved large body sizes and were apex predators in shallow marine environments during the Late Jurassic and Early Cretaceous in Europe and around the coast of the Tethys Seaway. Unfortunately, the origins of this clade are still poorly understood. 'Steneosaurus' obtusidens is a little-studied macrophagous species from the Oxford Clay Formation (Callovian, Middle Jurassic) of the UK and near Migné-les-Lourdines (Middle Callovian) in France. Despite being considered a sister taxon of the Late Jurassic taxon Machimosaurus, the taxonomy of 'S.' obtusidens remains unclear. Although three different synonymies have been proposed (variously a subjective synonym of other taxa), these taxonomic hypotheses have not been based on detailed anatomical comparisons and thus have not been tested. Here, we re-describe the holotype of 'S.' obtusidens, demonstrate that it is indeed a valid taxon, restrict the referred specimens to a fragmentary skeleton, nearly complete skull, and partial rostrum, and establish a new monotypic genus, Lemmysuchus. Our re-description reveals five autapomorphies for Lemmysuchus obtusidens and nine apomorphic characters that support the tribe Machimosaurini (Lemmysuchus + Machimosaurus).
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© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34 1
Zoological Journal of the Linnean Society, 2017, XX, 1–34. With 29 figures.
Re-description of ‘Steneosaurusobtusidens Andrews,
1909, an unusual macrophagous teleosaurid
crocodylomorph from the Middle Jurassic of England
MICHELA M. JOHNSON1,2*, MARK T. YOUNG2, LORNA STEEL3, DAVIDE FOFFA2,
ADAM S. SMITH4, STÉPHANE HUA5, PHILIPE HAVLIK6, ELIZA A. HOWLETT7 and
GARETH DYKE8,9
1Ocean and Earth Science, National Oceanography Centre, University of Southampton, European Way,
Southampton SO14 3ZH, UK
2School of GeoSciences, Grant Institute, The King’s Buildings, University of Edinburgh, James Hutton
Road, Edinburgh EH9 3FE, UK
3Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
4Nottingham Natural History Museum, Wollaton Hall, Nottingham NG8 2AE, UK
5Le Musée des Dinosaures d’Espéraza, 11260 Espéraza, France
6Zentrale Museumsentwicklung, Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25,
D-60325 Frankfurt am Main, Germany
7Earth Collections, Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
88MTA-DE Lendület Behavioural Ecology Research Group, Department of Evolutionary Zoology and
Human Biology, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary
9Center for Interdisciplinary Biosciences, Faculty of Science, Pavol Jozef Safarik University, Jesenna 5,
SK-04154 Kosice, Slovak Republic
Received 11 February 2016; revised 7 April 2017; accepted for publication 14 May 2017
Teleosaurids were a clade of crocodylomorphs that attained near-global distribution during the Jurassic Period. Within
Teleosauridae, one particular sub-clade of durophagous/macrophagous taxa achieved large body sizes and were apex
predators in shallow marine environments during the Late Jurassic and Early Cretaceous in Europe and around the
coast of the Tethys Seaway. Unfortunately, the origins of this clade are still poorly understood. ‘Steneosaurusobtusidens
is a little-studied macrophagous species from the Oxford Clay Formation (Callovian, Middle Jurassic) of the UK and near
Migné-les-Lourdines (Middle Callovian) in France. Despite being considered a sister taxon of the Late Jurassic taxon
Machimosaurus, the taxonomy of S.obtusidens remains unclear. Although three different synonymies have been proposed
(variously a subjective synonym of other taxa), these taxonomic hypotheses have not been based on detailed anatomical
comparisons and thus have not been tested. Here, we re-describe the holotype of ‘S.obtusidens, demonstrate that it is
indeed a valid taxon, restrict the referred specimens to a fragmentary skeleton, nearly complete skull, and partial rostrum,
and establish a new monotypic genus, Lemmysuchus. Our re-description reveals five autapomorphies for Lemmysuchus
obtusidens and nine apomorphic characters that support the tribe Machimosaurini (Lemmysuchus + Machimosaurus).
ADDITIONAL KEYWORDS: Crocodylomorpha – LemmysuchusMachimosaurusSteneosaurus – Teleosauridae –
Thalattosuchia.
INTRODUCTION
Teleosaurid crocodylomorphs were a near-globally
distributed clade that inhabited shallow marine and
brackish ecosystems throughout the Jurassic (Buffetaut
et al., 1981; Buffetaut, 1982a, b; Vignaud, 1993; Hua &
Buffetaut, 1997; Hua, 1999; Johnson et al., 2015) and
survived into the Early Cretaceous (Fanti et al., 2016;
Jouve et al., 2016). These animals are often viewed as
marine analogues of extant gavials because of their elon-
gate and tubular snout, dorsally directed orbits and high
*Corresponding author. E-mail: mickster4@shaw.ca
[Version of Record, published online 7 August 2017;
http://zoobank.org/ urn:lsid:zoobank.
org:pub:ADB5B0F9-7D9C-48CF-BBB6-1451BA209584]
2 M. M. JOHNSON ET AL.
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
tooth count, all of which suggest a primarily piscivorous
diet (Andrews, 1909, 1913; Buffetaut, 1982a, b). However,
within Teleosauridae, some taxa have been considered to
be durophagous and/or macrophagous, because they had
shorter snouts, proportionally enlarged supratemporal
fenestrae (i.e. increased jaw adductor musculature),
blunt tooth crown apices, serrated carinae and extensive
enamel ornamentation (Eudes-Deslongchamps, 1864,
1867, 1869; Andrews, 1909, 1913; Buffetaut, 1982a; Hua
et al., 1994; Hua & Buffetaut, 1997; Hua, 1999; Martin
& Vincent, 2013; Young & Steel, 2014; Young et al.,
2014a, b, 2015a, b; Fanti et al., 2016; Jouve et al. (2016).
The Late Jurassic–Early Cretaceous (Oxfordian
to Hauterivian) taxon Machimosaurus is the best-
studied macrophagous teleosaurid, known from both
cranial and postcranial remains and isolated teeth
from numerous countries (Sauvage & Liénard, 1879;
Krebs, 1968; see Young et al., 2014a for an overview).
Here, we use the taxonomy of Young et al. (2014a),
rather than that of Martin, Vincent & Falconnet
(2015) following the rationale of Foffa, Young &
Brusatte (2015) and because a new phylogenetic
analysis of Machimosaurus supports the multi-taxic
hypothesis (see Fanti et al., 2016). The sister taxon to
Machimosaurus, ‘Steneosaurusobtusidens Andrews,
1909, is a controversial taxon from the Middle Jurassic
of Europe. Over the past three decades, its validity
has been questioned, and three different subjective
species (both Machimosaurus and Steneosaurus) syn-
onymies have been proposed (see Adams-Tresman,
1987; Hua et al., 1994; Pierce, Angielczyk & Rayfield,
2009). Recent studies, however, have considered S.
obtusidens to be a distinct taxon (Martin & Vincent,
2013; Young et al. 2014a, 2015a). This taxonomic con-
fusion hinders our understanding of the origins of the
macrophagous teleosaurid sub-clade Machimosaurini.
Thus, the aim of this paper is to shed light on the
early evolution of durophagous/macrophagous teleosau-
rids by re-investigating the validity of ‘S.obtusidens.
We re-describe the holotype of S. obtusidens (which
consists of a complete cranium and mandible, and the
majority of the postcranial skeleton), demonstrate that
it is a valid taxon and establish a new monotypic genus,
Lemmysuchus obtusidens. We restrict the referred speci-
mens of this species to a fragmentary skeleton, a nearly
complete skull and a partial rostrum, and show that
most of the cranial and postcranial material previously
referred to ‘S.obtusidens belongs to other taxa. In addi-
tion, we assign three isolated teeth [two from the Oxford
Clay Formation (OCF) and one from the Cornbrash
Formation] to Machimosaurini indet. Finally, based on
the holotype and referred specimens, we conclude that S.
obtusidens was present in the Callovian OCF of England
and the Erymnoceras coronatum ammonite Zone (thus
being contemporaneous with the Peterborough Member
of the OCF) of Migné-les-Lourdines of France.
STENEOSAURUSOBTUSIDENS:
HISTORICAL BACKGROUND
Historical setting
The holotype of ‘S. obtusidens (Natural History
Museum, London, NHMUK PV R 3168) is part of
the Leeds Fossil Collection (Peterborough Member,
OCF; Middle Callovian) held at the NHMUK.
Charles Andrews established the name Steneosaurus
obtusidens for NHMUK PV R 3168 (Andrews, 1909)
when he described the Leeds Collection teleosaurids.
Later, Andrews (1913) tentatively referred two more
Leeds Collection specimens to ‘S.obtusidens (NHMUK
PV R 3169 and NHMUK PV R 3898). Andrews (1913)
listed no specific criteria for the referral of these two
specimens to ‘S.obtusidens and his decision may sim-
ply have been based on the large size and robustness
that both specimens share with the holotype. Andrews
(1913) later noted similarities between ‘S.obtusidens
and Steneosaurus durobrivensis Andrews, 1909, stat-
ing that (Andrews, 1913: 131): ‘if it were not for the
peculiarity of the teeth, [the former] might almost
have been referred to that species [S. durobrivensis]’.
The possibility that the ‘S.obtusidens morphotype
is a late ontogenetic variant of S. durobrivensis has
also been raised (Andrews, 1913; Steel, 1973) (note
that S. durobrivensis is now considered to be a subjec-
tive junior synonym of Steneosaurus edwardsi Eudes-
Deslongchamps, 1868; see Johnson et al., 2015).
The first worker to formally synonymize ‘S.
obtusidens with S. durobrivensis (=S. edwardsi) was
Adams-Tresman (1987). As noted by Young et al.
(2015a), the anatomical comparisons made between ‘S.
obtusidens and S. edwardsi (as S. durobrivensis) were
not based on the ‘S.obtusidens holotype (NHMUK
PV R 3168), but on referred specimens (i.e. NHMUK
PV R 3169, Peterborough Museum and Art Gallery,
Peterborough, PETMG R39 and PETMG R178). We
agree with Adams-Tresman (1987) that PETMG R39
matches the ‘S.obtusidens holotype (see Discussion).
However, the other two specimens lack the apomor-
phies of the ‘S.obtusidens holotype (see description
below), and thus cannot be referred to this taxon
(we argue that they instead should be referred to S.
edwardsi, see Discussion). This means that Adams-
Tresman’s (1987) discussion regarding tooth morphol-
ogy and dorsal osteoderm ornamentation were correct
and NHMUK PV R 3169 and PETMG R178 do indeed
belong to S. edwardsi. However, we show below that
these characteristics are distinct from those in the
S.obtusidens holotype, NHMUK PV R 3168. Young
et al. (2015a) also noted that Adams-Tresman (1987)
did not discuss the presence of three sacral vertebrae
in the ‘S.obtusidens holotype, while Andrews (1913:
132) considered it likely to be an ‘individual peculiar-
ity’ of the holotype. The neotype of Machimosaurus
STENEOSAURUSOBTUSIDENS 3
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
mosae Sauvage & Liénard, 1879 also has three sacral
vertebrae (Hua, 1999; Young et al., 2014a). Another set
of characteristics not mentioned by Adams-Tresman
(1987) are the pronounced socket-like reception pits
along the maxilla and dentaries for the opposing
tooth row. Again, this may have been due to Andrews
(1913: 131) being unsure if they were a natural char-
acteristic or a result of postmortem deformation.
However, this is another characteristic that the ‘S.
obtusidens holotype (NHMUK PV R 3168) shares
with Machimosaurus (Buffetaut, 1982b; Lepage et al.,
2008; Young et al., 2014a; note that Young et al., 2014a
considered vertically orientated, interlocking denti-
tion, with pronounced reception pits at the premaxil-
lary, maxillary and dentary interalveolar spaces to be
a Machimosaurus apomorphy). It is unclear whether
Adams-Tresman (1987) was being selective in what
characteristics the ‘S.obtusidens referred specimens
and the S. durobrivensis holotype and referred speci-
mens shared, or simply being cautious in regards to
morphologies unique to the ‘S.obtusidens holotype.
Steneosaurusobtusidens was also considered to
be a subjective junior synonym of the Kimmeridgian
species Machimosaurus hugii von Meyer, 1837 (Hua
et al., 1994; Hua, 1996, 1999). However, these authors
noted that the taxonomy of blunt-toothed teleosaurids
still required further study. More recently, Pierce et al.
(2009) suggested that ‘S.obtusidens, Steneosaurus
hulkei Andrews, 1913 and S. durobrivensis (all
Callovian taxa; the species S. edwardsi was not men-
tioned) were subjective junior synonyms of M. hugii.
This synonymy and corresponding species diagno-
ses have been criticized and rejected (see Martin &
Vincent, 2013; Young et al., 2014a; Johnson et al., 2015)
and, indeed, all phylogenetic analyses that include the
relevant taxa do not support any of the two proposed
synonymies (S. durobrivensis = S. edwardsi and M.
hugii). In these analyses,S.obtusidens is consistently
found to be the sister taxon of Machimosaurus, while
S. durobrivensis (=S. edwardsi) is the sister taxon to
this sub-clade (Young et al., 2012; Martin & Vincent,
2013; Young, 2014; Fanti et al., 2016; Young et al.,
2016a). Recent papers have agreed that S.obtusidens
is a distinct taxon (Martin & Vincent, 2013; Young
et al. 2014a, 2015a). Finally, Jouve et al. (2016) estab-
lished the tribe Machimosaurini for ‘S.obtusidens,
Machimosaurus and indeterminate Bathonian speci-
mens (based on shared craniodental morphologies; see
Introduction).
geological setting
The OCF is a Jurassic (Callovian – lower Oxfordian)
lithostratigraphic unit that is well known from exten-
sive exposures that extend from the western Dorset
coast to northern Yorkshire of England (Selden, Baker
& Phipps, 2008). The entire OCF is composed of two
main facies: the lowermost Peterborough Member and
an upper facies that comprises the Stewartby Member
and Weymouth Member (Cox, Hudson & Martill, 1992;
Martill et al., 1994; Selden et al., 2008).
The Peterborough Member, referred to in older lit-
erature as the Lower Oxford Clay, consists of compact
olive-coloured shaly clays and black and organic-rich
fissile shales (Hudson & Martill, 1994; Martill et al.,
1994). This member contains a diverse vertebrate
fauna, including: bony fish and chondrichthyans,
marine reptiles (ichthyosaurs, plesiosaurs, pliosaurs
and thalattosuchians) and rare dinosaur and pterosaur
remains (Martill et al., 1994). Oxygen isotope values
(Kenig et al., 1994) indicate that the OCF was depos-
ited in a shallow marine, open-shelf environment.
The Cornbrash Formation is a Bathonian–Callovian
(Middle Jurassic) lithostratigraphic unit that under-
lies the OCF (Wright, 1977). This stratigraphic section
consists of medium- to fine-grained limestone that is
bioturbated, yields many reptilian fossils and stretches
from the Weymouth area to the Scarborough area in
the UK (Cox & Sumbler, 2002), similar to the OCF. The
Cornbrash Formation is comprised of two main units,
the Cornbrash Limestone and the Cornbrash Shales,
which form a transgressional marine cycle (Wright,
1977). The Cornbrash Formation represents a section
of the Great Oolite Group (Sellwood et al., 1985).
Migné-les-Lourdines (the locality of specimen
LPP.M.21) is a small town just north of Poitiers, France.
The Coronatum Zone (ammonite zone named after E.
coronatum) in France is Middle Callovian (Brunet,
1969; Vignaud P, unpublished data) and corresponds
to the Peterborough Member of the OCF in the UK.
At Migné-les-Lourdines, this ammonite zone is repre-
sented by a white calcareous limestone (Brunet, 1969).
ABBREVIATIONS
institutional
CAMSM, Sedgewick Museum of Earth Sciences,
University of Cambridge, Cambridge, UK; DORCM,
Dorset County Museum, Dorchester, UK; GLAHM,
The Hunterian Museum, Glasgow, UK; GPIT,
Paläontologische Sammlung der Eberhard Karls
Universität Tübingen, Tübingen, Germany; LPP,
Institut de paléoprimatologie, paléontologie, humaine;
évolution et paléoenvironnements Université de
Poitiers, Poitiers, France; MNHN, Muséum national
d’histoire naturelle, Paris, France; NHMUK, Natural
History Museum, London, UK; NMS, Naturmuseum
Solothurn, Solothurn, Switzerland; NOTNH,
Nottingham Natural History Museum, Nottingham,
4 M. M. JOHNSON ET AL.
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
UK; OUMNH, Oxford University Museum of Natural
History, Oxford, UK;. PETMG, Peterborough Museum
and Art Gallery, Peterborough, UK; SMNS, Staatliches
Museum für Naturkunde Stuttgart, Baden-
Württemberg, Germany.
anatomical
XII, cranial nerve 12; ac dep, acetabular depression;
ac in, acetabular incision (acetabular notch); an, angu-
lar; ant f, anterior flange of second sacral vertebra; ant
pr, anterior process of ilium; ar, articular; art f, artic-
ular facet; atl, atlas; ax, axis; bas, basisphenoid; cen,
vertebral centrum; clp, lateral process of calcaneum;
cmp, medial process of calcaneum; cor, coronoid; cor gr,
coronoid groove; den, dentary; fm, foramen magnum;
fo, foramina; fr, frontal; ft, ‘fourth trochanter’ rugose
area; fem h, femoral head; fib, fibula; gf, glenoid fossa;
hc, humeral concavity; hs, humeral shaft; if, incisive
foramina; isch bl, ischial blade; jug, jugal; k, keel of
osteoderms; lac?, uncertain lacrimal area; le, lateral
epicondyle (of humerus); m con, medial condyle of
femur; me, medial epicondyle (of humerus); mx, max-
illa; mx gr, maxillary groove; na, nasal; ns, neural spine;
oc, occipital condyle; od, odontoid; or, orbit; pal, pala-
tine; par, parietal; pat, pathology; pit, ornamentation
pit on dorsal surface of osteoderms; pmx, premaxilla;
pmx1-2, first and second premaxillary tooth; pn, pubic
neck; po, postorbital; poz, postzygapophyses; pp, pubic
plate; prf, prefrontal; prz, prezygapophyses; pt, ptery-
goid; pub, pubis; q, quadrate; rib h, rib head; s1, first
sacral vertebra; s2, second sacral vertebra; s3, third
sacral (refers to first caudal) vertebra; spl, splenial;
sq, squamosal; st h, sternal head; sub r, sub-horizontal
anterior ridge of ilium; sup cr, supraacetabular crest of
ilium; sup occ, supraoccipital; supr fen; supratemporal
fenestra; san, surangular; tub, tuberculum; tp, trans-
verse process; t tub, tibial tuberosity; vac?, vacuity.
SYSTEMATIC PALAEONTOLOGY
crocodylomorpHa Hay, 1930 (sensu Nesbitt, 2011)
tHalattosucHia Fraas, 1901 (sensu Young &
Andrade, 2009)
teleosauridae geoFFroy Saint-Hilaire, 1831
macHimosaurini Jouve et al., 2016
macHimosaurini indeterminate
v 1905 Machimosaurus rigauxi Sauvage – Blake,
p. 26, Plate 1, fig. 5a–c
v 2014a Machimosaurus rigauxi Sauvage – Young
et al., p. 3
We have identified isolated teeth that have a character-
istic Machimosaurini dental pattern (see Lemmysuchus
description): GPIT/RE/301, CAMSM J64508 and
OUMNH J.14464. The first tooth crown GPIT/RE/301
(Fig. 12E–I) is from the OCF of Peterborough and was
excavated before 1906. It was sold to the Eberhard
Karls Universität in Tübingen, Germany, during the
first decade of the 20th century. A note in the collections
by E. Buffetaut in 1981 suggested that it could be ‘S.
obtusidens, while another specimen note by B. Stürtz (a
commercial fossil collector from Bonn) suggested that
it might belong to Machimosaurus but was similar to
the genus Steneosaurus. The tooth is conical, robust
with a blunt apex and posteriorly curved. The majority
of the root is missing. The tooth is single-cusped and
has no accessory cusps or cingula. The enamel ridges
are well defined and pronounced and are close in par-
allel vertical rows. The enamel ornamentation is simi-
lar to the L. obtusidens holotype (NHMUK PV R 3168),
with randomly arranged ridges near the apex that are
straight, parallel and closely packed together towards
the root of the tooth.
Another isolated tooth, CAMSM J64508 (Fig. 12J–
P), was collected in Fletton (Cambridgeshire) and is
also possibly from the Leeds Collection. It has origi-
nally been regarded (by whom is unknown) as a plio-
saurid of the genus Simolestes, most likely for its size.
However, the curvature, blunt apex, presence of pro-
nounced carinae and ornamentation patterns distin-
guish it from any late Middle Jurassic pliosaurids. The
tooth is conical and has a circular cross-section which
is maintained through the whole apicobasal length. As
typical in Machimosaurus and L. obtusidens, the tip of
the crown is blunt (Young et al., 2014a, b). The consid-
erable size of the crown (~5 cm apicobasal length) and
the height-to-length ratio suggests CAMSM J64508
may be one of the large dentary or premaxillary pseu-
docaniniform teeth. The crown is clearly ornamented
by long continuous and evenly spaced apicobasal
ridges that occur with the same density on the labial,
mesial and lingual sides. As in Machimosaurus and L.
obtusidens, the ornamental ridges on the apex become
shorter until they form the characteristic anastomosed
pattern (Young et al., 2014a, 2015a, b). Interestingly,
this ornamentation pattern is convergent with the
Late Jurassic metriorhynchid Torvoneustes carpen-
teri (Wilkinson,Young & Benton, 2008). In CAMSM
J64508, the carinae are present although almost indis-
tinguishable for most of the crown length (Fig. 12J–P).
However, they can be observed in the apical ‘anastomo-
sed region’. The carinal keel is considerably clearer on
one side than the other. The ornamentation pattern of
the apex contacts the carinae forming false serrations
(Young et al., 2015a).
Tooth OUMNH J.14464 (Fig. 12Q–T) is from the
Cornbrash Formation and was figured by Blake as
Machimosaurus rigauxi Sauvage, 1879 (Blake, 1905:
26: Plate 1, fig. 5a–c). The crown of this tooth is intact
and the root is missing. The apex is slightly pointed
STENEOSAURUSOBTUSIDENS 5
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
and the entire tooth is conical and mediolaterally
thickened. The mesial and distal carinae are faint, not
as pronounced as in GPIT/RE/301, and when viewed
with the naked eye terminate in the middle of the
tooth. The numerous enamel ridges run ventrally
parallel and close together. At the apex, the ridges
are disoriented and extend in random patterns, much
as how Andrews (1913) described the teeth of the
L. obtusidens holotype (NHMUK PV R 3168).
The two tooth crowns from the OCF (GPIT/
RE/301 and CAMSM J64508) may be referable to
L. obtusidens. However, as they are isolated crowns, we
refrain from making that assignment. The M. rigauxi
tooth (OUMNH J.14464) is interesting as it is from the
Cornbrash Formation, a lithostratigraphic unit that L.
obtusidens is currently not known from.
Lemmysuchus gen. nov.
(Figs 1–21)
urn:lsid:zoobank.org:act:83D7C69A-4009-478E-
8D6E-A05F39E190D1
Type species
Steneosaurus obtusidens Andrews, 1909 [following rec-
ommendation 67B of the International Commission on
Zoological Nomenclature (ICZN) code]. Now referred to
as Lemmysuchus obtusidens (Andrews, 1909) comb. nov.
Diagnosis
Same as the only known species (monotypic genus).
Etymology
‘Lemmy’s crocodile’. Lemmy referring to Ian Fraser
Kilmister, better known as ‘Lemmy’, the deceased
founder, bassist and lead singer of Motörhead, and
suchus is the Latinized form of the Greek soukhos
(σοῦχος), meaning crocodile.
Lemmysuchus obtusidens (andrews, 1909)
comb. nov.
urn:lsid:zoobank.org:act:83D7C69A-4009-478E-
8D6E-A05F39E190D1
v* 1909 Steneosaurus obtusidens Andrews, p. 306,
Plate 9 figure 2
v 1913 Steneosaurus obtusidens Andrews – Andrews,
p. 130, Text-fig. 50, Plate 7 all figures (partim)
v 1969 Steneosaurus cf heberti Morel de Glasville –
Brunet, Plate 1 figure b-b (LPP.M.21)
v 1973 Steneosaurus obtusidens Andrews – Steel,
p. 33, figure 13.13
v 1987 Steneosaurus durobrivensis Andrews –
Adams-Tresman, p. 205 (partim)
1993 Steneosaurus cf heberti Morel de Glasville
– Vignaud
v 1994 Machimosaurus hugii von Meyer – Hua
et al., p. 15 (partim)
v 1996 Machimosaurus hugii von Meyer – Hua,
p. 1562 (partim)
v 2009 Machimosaurus hugii von Meyer – Pierce
et al., p. 1085 (partim)
v 2013 Steneosaurus obtusidens Andrews – Martin
& Vincent, p. 192
v 2014a ‘Steneosaurusobtusidens Andrews – Young
et al., p. 3
v 2014b Steneosaurusobtusidens Andrews – Young
et al., p. 2
v 2016 Steneosaurusobtusidens Andrews – Jouve
et al., p. 4
Holotype
NHMUK PV R 3168, complete cranium and mandible
in articulation, atlas–axis complex, 6 postaxial cervi-
cal vertebrae, 14 dorsal vertebrae, 3 sacral vertebrae,
21 caudal vertebrae, 1 complete cervical rib and 20
cervical rib fragments, 49 dorsal rib fragments (fewer
than 5 complete ribs), 2 gastralia fragments, 1 right
scapula, 1 distal fragment of a humerus, 1 ulna, 1 right
ilium, both ischia, 1 pubis, both femora, 1 tibia, possi-
ble pieces of fibulae or carpals/tarsal elements, 5 ankle
bones (including a calcaneum, distal tarsal and astra-
galus), 4 phalanges, numerous dermal osteoderms
(~56), 33 isolated teeth and numerous bone fragments
(Figs 1–3, 12A–D, 1321).
Etymology
‘Lemmy’s blunt-toothed crocodile’. From the Latin for
blunt (obtusus) and tooth (dens). Named for the blunt
apices of the teeth.
Type locality
Peterborough, England, UK. The exact age and area of
collection of this specimen is not known, original Leeds
Collection Number 6.
Type horizon
Peterborough Member, OCF, Ancholme Group. Middle
Callovian, Middle Jurassic.
Referred specimens
PETMG R39, largely incomplete rostrum, fragment of
right mandibular ramus, partial dorsal osteoderm
6 M. M. JOHNSON ET AL.
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and five dorsal vertebral centra. PETMG R31, five
vertebral centra (two dorsals and three sacrals),
are associated with PETMG R39 and very likely
belong to the same individual (see Discussion)
(Peterborough Member, OCF, Ancholme Group;
Middle Callovian).
LPP.M.21, nearly complete skull (left lateral portion
not preserved from the orbit to the squamosal) and
mandible (anterior region is preserved) (E. corona-
tum ammonite Zone, Middle Callovian).
NOTNH FS3361, partial rostrum, including the pre-
maxillae and part of the maxillae (horizon and
locality unknown, thought to be OCF because of the
state of preservation).
Emended diagnosis
Teleosaurid crocodylomorph with the following
unique combination of characters [proposed auta-
pomorphic characters are indicated by an asterisk
(*)]: the rostrum external surface is strongly convex,
in particular the nasals*; partial or complete fusion
of the internasal suture*; axis lacks diapophyses
(shared with Steneosaurus bollensis Jaeger, 1828; see
Westphal, 1962); the ilium anterior process is small
and anteroposteriorly shortened*; on the ilium the
acetabulum is shallow and poorly developed*; shal-
low supraacetabular crest on the ilium*; the dorsal
osteoderm ornamentation is composed of small-to-
large, irregularly shaped pits that radiate from the
centre of the keel and are arranged in a starburst
pattern (to a certain extent similar to M. mosae; Hua,
1999; Young et al., 2014a)*.
Characteristics shared with Machimosaurus
Lemmysuchus obtusidens shares the following nine
synapomorphies with Machimosaurus (sensu Young
et al., 2014a): (1) conical teeth with blunt/rounded api-
ces; (2) tooth enamel ornamentation varies along the
crown, that is, in the basal region enamel ornamen-
tation is composed of numerous apicobasally aligned
ridges of high relief, which transition into an anasto-
mosed pattern in the apical region; (3) teeth have true
and false denticles on the carinae; (4) ratio of crown
apicobasal height to basal transverse width can be as
low as 1.8 in the posterior teeth; (5) pronounced socket-
like reception pits along the maxilla and dentaries for
the opposing tooth row; (6) the supratemporal fossae
are parallelogram-shaped in dorsal view; (7) three
sacral vertebrae; (8) ischial blade posterior margin is
blunt and sub-square in shape and (9) proximal tibia
strongly deflects anteriorly.
However, L. obtusidens lacks the following eight
Machimosaurus autapomorphies (sensu Young
et al., 2014a; note that the two axis neural spine
autapomorphies cannot be determined in L. obtusidens
due to preservation):
1. Three alveoli per premaxilla (L. obtusidens has four
alveoli per premaxilla).
2. The first premaxillary alveoli are orientated
strongly anteroventrally (L. obtusidens lacks this
condition).
3. 18–22 alveoli per maxilla (L. obtusidens has at least
29 alveoli per maxilla).
4. 19–25 alveoli per dentary (L. obtusidens has ~29
alveoli per dentary).
5. Presence of carinae is variable in Machimosaurus
spp. (in L. obtusidens all teeth have carinae).
6. The rostrum is broad and mesorostrine, constitut-
ing fewer than 60% of the basicranial length (in
L. obtusidens, the rostrum is 61.2% of basicranial
length and is less broad, thus falling slightly out-
side the condition seen in Machimosaurus).
7. Ratio of maximum supratemporal fossa length
to basicranial length is greater than 27% (in
L. obtusidens, this ratio is 25.8%).
8. Medial quadrate hemicondyle is consider-
ably smaller than the lateral hemicondyle (in
L. obtusidens both condyles are large and similar in
size).
Lemmysuchus obtusidens (NHMUK PV R3168),
Machimosaurus, Steneosaurus heberti Morel de
Glasville, 1876 (MNHN.F 1890-13) and S. edwardsi
(NHMUK PV R3701) share three characteristics:
(1) anterior processes of the jugals are very elongate
and slender, so that they largely restrict a lacrimal-
maxilla contact on the external surface, except for
the anterolateral margins of the lacrimals which
do contact the maxillae (Fig. 6); (2) the Meckelian
canal (=groove) is not deeply excavated on the dor-
sal surface of the splenials (Fig. 9) in contrast to
other thalattosuchians such as Steneosaurus leedsi
Andrews, 1909 (NHMUK PV R3320) and (3) the
closure of the antorbital fenestrae (Fig. 22D–G)
(see description below on how we conclude that
L. obtusidens lacks these fenestrae). Note that
Young et al. (2014a) listed the absence of antorbital
fenestrae was shared by Machimosaurus (SMNS
91415) and S. heberti. Lemmysuchus obtusidens
also shares one characteristic with S. heberti
(MNHN.F 1890-13); sharp dorsoposterior curva-
ture of the posterior mandibular rami (as opposed
to gradual curvature in S. edwardsi) (PETMG 178)
(Fig. 22A–C).
Character note
Lemmysuchus obtusidens has two characteristics that
are well developed in the holotype but not clear in
other OCF teleosaurid specimens (because of the typi-
cally poor preservation of skulls, through dorsoventral
STENEOSAURUSOBTUSIDENS 7
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crushing and/or shearing). These are: (1) a large nuchal
crest on the supraoccipital and (2) large and pronounced
paired occipital tuberosities (somewhat similar to those
seen in dyrosaurid crocodyliforms, which are developed
to a much greater extent; e.g. MNHN.F ALG 1). These
characteristics, albeit in a reduced form, are also seen
in Teleosaurus cadomensis Lamouroux, 1820 (MNHN
cast of an adult skull, MNHN.F AC 8746; Jouve, 2009),
S. heberti (MNHN.F 1890-13) and Machimosaurus
buffetauti Young et al., 2015 (SMNS 91415; Martin &
Vincent, 2013; Young et al., 2014a).
Description
The holotype of L. obtusidens, NHMUK PV R 3168,
comprises a nearly complete skeleton (Figs 1–3, 12A–
D, 1321) (Andrews, 1909, 1913). The cranium and
mandible adhere together so tightly that the cranium
palatal view and mandible dorsal view is inaccessible;
LPP.M.21, however, preserves the palatal view, which
is easily accessible (Fig. 8C, D), and NOTNH FS3361
preserves part of the rostrum, including the premax-
illae (Figs 10, 11). The cranium has experienced dor-
soventral compression and has numerous fractures
making it difficult to discern sutures from breaks.
However, PETMG R39 is well preserved (Figs 4–6),
and the preorbital area, cranium palatal surface and
part of the mandibular dorsal surface can be described
from this specimen.
Cranium: The cranium of L. obtusidens (NHMUK
PV R 3168) (Figs 1–3) is ~1.4 m long (Andrews,
1909, 1913). It is similar to Machimosaurus in terms
of overall anatomy and robusticity. The rostrum is
more robust but comparatively shorter than those of
other Middle Jurassic teleosaurids (e.g. S. leedsi, S.
heberti, Mycterosuchus nasutus) (Andrews, 1913) and
comprises 61.2% of the total skull length [the 51% ratio
given in Andrews (1913) was a typographical error].
The anterior premaxilla and dentaries are laterally
expanded as in other teleosaurids (e.g. Andrews, 1909,
1913; Hua, 1999; Martin & Vincent, 2013; Young et al.,
2014a). In NHMUK PV R 3168 (Fig. 1), the preorbital
region is deformed, possibly due to an infection of the
bone caused by a bite (there is a large tooth deeply
embedded in this region of the cranium). Conversely,
PETMG R39 (Figs 4, 5) and LPP.M.21 (Fig. 8A, B) are
well preserved in this area. Based on NHMUK PV R
3168 (Figs 1–3), LPP.M.21 (Fig. 8) and PETMG R39
(Figs 4, 5), the orbits would have been large, oval in
shape and oriented more anteroposteriorly than in
most other teleosaurids (such as S. leedsi NHMUK PV
R 3806). In dorsal view, the supratemporal fenestrae
(Fig. 1) are considerably longer than wide and are
considerably longer than the orbits. The cranial
description refers to the holotype (NMHUK PV R
3168) unless otherwise specified. Due to the fragility
and heaviness of the NHMUK PV R 3168 cranium,
the authors were unable to flip it over to observe the
palates. Therefore, all information pertaining to the
palatal surface comes from LPP.M.21.
Premaxillae: The premaxillae (Figs 1, 2, 3A, C)
are large and robust, surround the external narial
Figure 1. Photograph (A) and line drawing (B) of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK PV
R 3168, holotype. Skull in dorsal view with additional details of the premaxillary dentition. Refer to the main text for the
abbreviations list. Scale bar: 20 cm.
8 M. M. JOHNSON ET AL.
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opening and face anterodorsally. The external nares
are laterally expanded and their posterior margins
do not reach beyond the third premaxillary alveolar
pair. The anterior two-thirds of the premaxilla
is laterally expanded and the anterior margin
is ventrally deflected, giving the snout a scoop-
like appearance. In LPP.M.21 (Fig. 8A, B) and
NOTNH FS3361 (Figs 10, 11), the incisive foramen
(=naso-oral fenestra) is very small and is situated
in the middle of the suture of the premaxillae. In
dorsal view, the premaxilla–maxilla suture is well
developed and W-shaped. The left premaxilla–
maxilla suture is directed proximodistally parallel
towards the middle of the rostrum with two small,
pointed, posterior-oriented processes edges in dorsal
view. The premaxilla contains four teeth, with the
fourth (posterior-most) being the largest. The first
two premaxillary alveoli are nearly confluent,
with a thin interalveolar lamina separating them.
The interalveolar lamina is missing in NOTNH
FS3361 and LPP.M.21, making it appear as though
there were only three premaxillary teeth present
(this feature is noted in Vignaud, 1997). There is
a diastema between the last premaxillary tooth
and the first maxillary tooth. In life, large dentary
caniniform teeth would have been present (as
in Machimosaurus and other large teleosaurids;
Andrews, 1909, 1913; Martin & Vincent, 2013).
Maxillae: The maxillae (Figs 1, 2, 3A, C) form a
substantial part of the rostrum. Their lateral margins
are sub-parallel in dorsal view. The maxilla separates
the nasals from the premaxillae. The precise maxillary
tooth count is difficult to determine but there are
~29 alveolar pairs (Andrews, 1913). The specimen
LPP.M.21 has 29 alveolar pairs (Fig. 8C, D) and
NOTNH FS3361 preserves ~26 alveolar pairs (the
posterior portion of the maxilla is missing) (Fig. 10E,
F). The lateral surface of the maxilla is ornamented
by well-spaced, deep foramina that are visible in both
dorsal, lateral and anterior views (Figs 1, 2, 3A, B). The
maxillary tooth row ends anterior to the anterior-most
border of the sub-orbital fenestra. Numerous, deep
reception pits for dentary teeth are along the middle
and anterior regions of the ventral-lateral margin of
the maxillae (Fig. 2). The posterolateral regions of
both maxillae in PETMG R39 have a groove which
follows approximately parallel with the long anterior
process of the jugal (Figs 4–6). This feature is shared
with Machimosaurus, S. heberti (MNHN.F 1890-13)
and S. edwardsi (Martin & Vincent, 2013; Young et al.,
2014a). There is a small pathology on the ventral right
maxilla in NOTNH FS3361 (Fig. 10).
Jugals: The jugals are triradiate and form the lateral
border of the orbit (Figs 1, 2, 4–6, 8A, B) as in other
teleosaurids (Andrews, 1909, 1913). The jugal is
Figure 2. Photograph (A, C) and line drawing (B, D) of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK
PV R 3168, holotype. Skull in left (A, B) and right (C, D) lateral views. Refer to the main text for the abbreviations list. Scale
bar: 20 cm.
STENEOSAURUSOBTUSIDENS 9
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dorsally compressed by the postorbital-squamosal
and is ventrally compressed by the dentary due to
poor preservation. The anterior margin of the jugal
runs between the lacrimal and posterior regions of the
maxilla (Figs 2, 3A, C). This feature is shared among
S. edwardsi (PETMG R175), S. heberti (MNHN.F
1890-13), L. obtusidens (PETMG R39) (Figs 4–6),
M. hugii (NMS 7012) and possibly also M. buffetauti
(the holotype SMNS 91415 is poorly preserved in
this region). However, it is only in Lemmysuchus and
Machimosaurus that the jugal is extremely elongate, it
anteriorly extends and reaches the anterior end of the
lacrimal. The postorbital-jugal or quadratojugal-jugal
contacts cannot be seen clearly in NHMUK PV R 3168,
as the specimen is crushed in those areas. In LPP.M.21,
the postorbital-jugal contact is anteroposteriorly
straight (Fig. 8A, B). The quadratojugal-jugal contact
is not clear in either NHMUK PV R 3168 or LPP.M.21.
Nasals: The nasals (Figs 1, 2, 3A, C) are large
triangular bones exposed on the dorsal surface of
the posterior rostrum and orbital area. Both nasals
(in NHMUK PV R 3168) are missing their anterior
and posterior regions. The nasal anterior processes
extend past the third maxillary tooth. Deformation,
due to an embedded tooth previously mentioned
from another animal (which is circular and has left a
striated impression behind), obscures the view of the
anterior region of the nasal anterior processes. The
nasals have a little ornamentation, consisting of faint
ridges. There is a faint internasal midline suture on
the anterior rostrum; further posteriorly there is no
internasal suture, suggesting the nasals are partially
or completely fused. This is seen in NHMUK PV
R 3168 as well as LPP.M.21 (Fig. 8A, B), NOTNH
FS3361 (Fig. 10A, B) and PETMG 39 (Fig. 4A, B).
Both nasals form the beginning of a dorsally directed
‘dome’ towards the medial contact with the frontal.
PETMG 39 (Figs 4, 5) and NOTNH FS3361 (Fig. 10)
show the beginning of the ‘dome’ in the anterior nasals
(as the posterior nasals are not preserved in NOTNH
FS3361). In LPP.M.21 (Fig. 8A, B), it is not clear if
the nasals are convex (due to dorsoventral crushing,
although this could be an ontogenetic feature), and the
nasal anterior processes are approximately one-third
of the posterior rostrum and have well-developed near-
parallel suture contacts with the maxillae.
Prefrontals: The prefrontals (Figs 1, 2) are slightly
sub-circular in dorsal view and form the anteromedial
border of the orbits. The prefrontal contacts the nasal
medially and the lacrimal laterally. The frontal-
prefrontal contact cannot be clearly seen even in the
better preserved PETMG R39 due to breaks in this
area (Figs 4–6). In LPP.M.21 (and to some extent on
the right side in NOTNH FS3361), the prefrontal
Figure 3. Photograph (A, B) and line drawings (C, D) of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK
PV R 3168, holotype. Skull in anterior (A, C) and occipital (B, D) views. Refer to the main text for the abbreviations list.
Scale bar: 10 cm.
10 M. M. JOHNSON ET AL.
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contacts the frontal posteromedially at a straight angle
(Figs. 8A, B). The prefrontals are well developed and
tear-shaped (Figs. 8A, B, 10).
Lacrimals: The lacrimals are better preserved in
PETMG R39 (Figs 4–6) and LPP.M.21 (Fig. 8A, B)
than in NHMUK PV R 3168 (Figs 1, 2) even though
the medial and posterior margins are not preserved
well. The lacrimals are large and triangular as in other
teleosaurid taxa (Andrews, 1909, 1913) and constitute
most of the anterior-lateral border of the orbits.
Andrews (1913) reported paired openings ~5–7 cm
anterior to the lacrimal in NHMUK PV R 3168 that he
considered to be antorbital fenestrae, describing them
as no more than 5 cm in length and longer than wide
(Andrews, 1913). PETMG R39 (Figs 4–6), NOTNH
FS3361 (Fig. 10) and LPP.M.21 (Fig. 8A, B) show that
L. obtusidens did not have antorbital fenestrae. As
such, we interpret these ‘openings’ in NHMUK PV R
3168 to be cracks caused by compression.
Figure 4. Photograph (A, C) and line drawing (B, D) of PETMG R39, referred to as Lemmysuchus obtusidens (Andrews,
1909) comb. nov. Skull in dorsal (A, B) and palatal (C, D) views. Refer to the main text for the abbreviations list. Scale bar:
10 cm.
STENEOSAURUSOBTUSIDENS 11
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Frontal: The frontal (Figs 1, 2, 3A, C) is a large and
deep (dorsoventrally thickened) bone with no evidence
of a midline suture. The anterior region slightly
slopes anteriorly in conjunction with the posterior
nasal and descends posteriorly, giving it a ‘domed’
appearance (Figs 2, 3A, C). The anterior process is not
preserved; however, it is well preserved in LPP.M.21
(Fig. 8A, B), showing that it is as short as in most
other teleosaurids (e.g. S. leedsi; see Andrews, 1913).
The frontal contributes to the posteromedial border
of the orbits (Figs 1, 2) and is well seen in LPP.M.21
(Fig. 8A, B). The frontal forms a straight vertical
contact with the postorbital in dorsal view and forms
the anterior medial borders of the supratemporal
fenestrae. The ornamentation on the frontal does
not differ from other OCF teleosaurids and consists
of pronounced irregular ridges radiating from the
centre of the bone.
Postorbitals: The large, robust postorbitals (Figs 1,
3A, C) form the lateral and part of the posteroventral
border of the orbits. In lateral view, the dorsoventral
suture of the postorbital contacts the squamosal and
the left postorbital strongly contacts the frontal and
forms the posterior margin of the orbit. Because both
postorbitals are broken, the postorbital bars are not
preserved in NHMUK PV R 3168. In LPP.M.21, the
postorbital bar is similar to other OCF teleosaurids
(Fig. 8A, B). It forms the posterior margin of the orbit,
is slightly anteroposteriorly thickened and of standard
mediolateral length.
Parietal: The unornamented parietal (Figs 1, 2, 3A, C)
is a single bone with no trace of a midline suture that
contributes to the medial and posterior borders of the
supratemporal fenestrae. Dorsally the parietal does
not overhang the occipital condyle. The parietal bar is
relatively thin and anteroposteriorly elongated. The
posterior region of the parietal is anteriorly concave.
In LPP.M.21, there is little to no ornamentation on the
parietal (Fig. 8A, B).
Squamosals: The squamosals (Figs 2, 3B, D) are large,
anteroposteriorly elongate, L-shaped bones and are
Figure 5. Photograph (B, D) and line drawing (B, D) of PETMG R39, referred to Lemmysuchus obtusidens (Andrews, 1909)
comb. nov. Skull in left (A, B) and right (C, D) lateral views. Refer to the main text for the abbreviations list. Scale bar: 10 cm.
12 M. M. JOHNSON ET AL.
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well preserved in LPP.M.21 (Fig. 8A, B). The squamosal
forms the posterolateral border of the supratemporal
fenestrae and its posterolateral surface is concave. It
contacts the quadrate posteroventrally in lateral view.
The squamosal bar is robust and anteriorly contacts the
postorbital bar (together forming the supratemporal
arch). In NHMUK PV R 3168, the left squamosal is
distorted and flattened due to poor preservation.
Quadrates: The quadrates (Figs 1, 3B, D) are large,
robust and are strongly sutured to the squamosals
and quadratojugals. The anterodorsal region of the
quadrate contacts the squamosal and quadratojugal
while the posteroventral margin articulates with
the angular (=jaw joint) and medially contacts the
exoccipital. The posteroventral lateral and medial
hemicondyles are approximately the same size and
length. They are both elongated mediolaterally, are
oval in shape and have rounded posterior edges.
In occipital view, the hemicondyles posteriorly
extend further than the exoccipitals. The right
quadrate is well preserved while the left quadrate
is not. In LPP.M.21, the quadrates are large and
mediolaterally expanded in ventral view (Fig. 8C, D).
Quadratojugals: The quadratojugals are dorsally and
ventrally compressed and are not visible in dorsal view.
The posterior region of the quadratojugal is expanded
mediolaterally to accommodate the quadrate and
extends slightly further than the outermost tip of the
quadrate.
Figure 6. Close-up of right lateral view of PETMG R39,
referred to Lemmysuchus obtusidens (Andrews, 1909)
comb. nov, showing in detail the maxilla, jugal, nasal and
lacrimal bones. Outlines the jugal-maxilla and lacrimal-jugal
contacts. Note the absence of antorbital fenestrae. Refer to
the main text for the abbreviations list. Scale bar: 5 cm.
Figure 7. Partial mandible section of PETMG R39, referred to Lemmysuchus obtusidens (Andrews, 1909) comb. nov.,
in (A) dorsal, (B) lateral, (C) ventrolateral, (D) ventral and (E) anterior views. Refer to the main text for the abbreviations
list. Scale bar: 10 cm.
STENEOSAURUSOBTUSIDENS 13
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Figure 8. Photographs (A, C) and line drawings (B, D) of LPP.M.21, referred to Lemmysuchus obtusidens (Andrews, 1909)
comb. nov. Skull in dorsal (A, B) and palatal (C, D) views. Refer to the main text for the abbreviations list. Scale bar: 10 cm.
Figure 9. Photograph (A) and line drawing (B) in dorsal view of the mandibular interior of LPP.M.21, referred to
Lemmysuchus obtusidens (Andrews, 1909) comb. nov. Refer to the main text for the abbreviations list. Scale bar: 10 cm.
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Ectopterygoids: Only the right ectopterygoid is
preserved in NHMUK PV R 3168. Anteriorly it contacts
with the maxilla. The contact with the pterygoids and
palatines cannot clearly be seen. The dorsal surface
of the ectopterygoid is slightly concave. The right
ectopterygoid is preserved in LPP.M.21 and curves
ventromedially (Fig. 8A, B).
Supraoccipital: The supraoccipital is positioned
ventral to the parietal and is only visible in occipital
view (Fig. 3B, D). The ventral edge is not triangular
but curved so it appears as two ‘lobes’ (Fig. 3). A large
nuchal crest (Fig. 3B, D) is situated directly in the
middle of the supraoccipital.
Exoccipital: The exoccipitals make up the majority of
the occipital surface of the cranium. The right side has
been medially compressed and the dorsal rim curves
medially, while the left side tilts dorsally and flares
mediolaterally. The exoccipitals are dorsally expanded
Figure 10. Dorsal (A, B), left lateral (C, D), ventral (E, F) and right lateral (G, H) photographs and line drawings of NOTNH
FS3361, referred to Lemmysuchus obtusidens (Andrews, 1909) comb. nov. Refer to the main text for the abbreviations
list. Note the small incisive foramina and the number of alveoli in the premaxillae and maxilla. Scale bar: 10 cm.
STENEOSAURUSOBTUSIDENS 15
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above the foramen magnum, as in M. buffetauti and M.
mosae (Hua, 1999; Martin & Vincent, 2013). Laterally,
the exoccipitals descend rapidly, so in occipital
view, they appear almost box-like. The exoccipitals
contribute to the occipital condyle. The paraoccipital
processes are small and the lateral wings are elongate
and robust. The foramen for cranial nerve XII is small
and parallel to the foramen magnum (Fig. 3B, D).
Basioccipital: The basioccipital contributes to the
ventral region of the foramen magnum and is slightly
wider than tall. The occipital condyle is larger and
more circular than the foramen magnum. In ventral
view (LPP.M.21), two well-developed and slightly
anteroposteriorly elongated basioccipital tuberosities
are visible, with the left one being larger due to
variable preservation (Fig. 8C, D).
Pterygoid: The right pterygoid wing is present in
the holotype (NHMUK PV R 3168), but it is poorly
preserved; it is unclear how complete the pterygoid
wing is in this specimen without access to the palatal
view. The left pterygoid is similarly broken but the
lateral pterygoid wing is accessible laterodorsally. It is
large and elongated craniocaudally and lateromedially.
The dorsal surface of the wing is concave and the
posterior region curves anteromedially, possibly due to
breakage. In ventral view (LPP.M.21), the pterygoid is
thin and elongated and contributes to the medial and
posterior borders of the sub-orbital fenestrae, which
are tear-shaped (thin anteriorly, wide and slightly
rounded posteriorly) (Fig. 8). In LPP.M.21, the anterior
process of the pterygoid articulates with the palatines
(Fig. 8C, D).
Palatines: All information from the palatines comes
from LPP.M.21 and PETMG R39. The palatines
(Fig. 8C, D) are dorsoventrally thin, elongate bones
and are similar in form to other teleosaurids, such
as S. leedsi (NHMUK PV R 3806) (Andrews, 1913).
In LPP.M.21, the anterior regions of both palatines
are not preserved and both posterior regions are
slightly deformed; however, PETMG R39 preserves
the anterior palatines that are slightly rounded,
have small anterior processes and articulate with
the posterior processes of the maxillae (Fig. 4C, D).
The palatines contact one another along the skull
midline until posteriorly they are separated by
the anterior process of the pterygoid. The anterior
extensions of the palatine are nearly parallel to the
maxillary tooth row, similar to M. buffetauti (Martin
& Vincent, 2013).
Basisphenoid: The anterior surface of the basisphenoid
(LPP.M.21) is deformed (Fig. 8C, D). This structure has
two elongated posterolaterally directed processes and
comes into posterior contact with the quadrate.
Other elements: The proötic and laterosphenoid are
not visible in dorsal or ventral views, and as a result
we could not properly describe these bones.
Mandible: The mandible of NHMUK PV R 3168 is
diagenetically deformed and attached to the cranium
so that the dorsal surface is not visible. The mandibular
symphysis measures ~58 cm, contributing ~42.3% of
the entire length (Young et al., 2015a). Among other
specimens, only a short segment of the right mandibular
ramus in PETMG R39 is preserved and it clearly
shows the contact among the dentary, angular and
splenials to be posterior to the mandibular symphysis
on the ventral side. The majority of the mandible is
also preserved in LPP.M.21, as the posterior-most
areas are missing. Our mandibular description refers
Figure 11. Ventral close-up of (A) photo and (B) line drawing of NOTNH FS3361, referred to Lemmysuchus obtusidens
(Andrews, 1909) comb. nov. Refer to the main text for the abbreviations list. Scale bar: 10 cm.
16 M. M. JOHNSON ET AL.
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to the holotype (NHMUK PV R 3168) unless otherwise
specified.
Dentary: The dentary (Figs 1, 2, 3A, C) is a long major
element of the lateral surface of the lower jaw, as in
the majority of crocodylomorphs. The anterior end of
the dentary is spatulate and laterally enlarged as in
Machimosaurus (Young et al., 2014a). There are ~29
(possibly one or two more alveoli) alveoli per dentary
(at least 25 alveoli per dentary in LPP.M.21) of which
Figure 12. Isolated tooth crowns of Lemmysuchus obtusidens (Andrews, 1909) comb. nov. NHMUK PV R 3168 (holotype)
in (A) mesial view and (B) lingual close-up view and PETMG R39 (C, D) close-up detailed view of erupting tooth. Isolated tooth
crowns referred to Machimosaurini indet.: GPIT/RE/301 [in E (posterior), F (labial), G (anterior), H (lingual) and I (dorsal)
views)]; CAMSM J64508 [in J (posterior), K (labial), L (anterior), M (lingual), N (dorsal) views, O (ventral) and P (apex close-
up) views]; OUMNH J.14464 [in Q (posterior), R (labial), S (anterior) and T (lingual) views]. Scale bar: (A) 2 cm; (B–T) 1 cm.
STENEOSAURUSOBTUSIDENS 17
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~22–24 are adjacent to the mandibular symphysis
(Andrews, 1913; Young et al., 2015a). Many of the
teeth are missing but those still in situ are well
preserved and complete. The four anterior-most teeth
are elevated dorsally when compared to the rest of
the tooth row, as normally seen in teleosaurids such
as S. leedsi (Andrews, 1913). The dentition is strongly
heterodont compared to other teleosaurids; the teeth in
the anterior region are large and have a higher crown
base to length ratio, whereas the posterior crowns
are characterised by a lower ratio. The interalveolar
distance is generally smaller than half the alveolar
length but always longer than a quarter of the alveolar
length.
Surangular and angular: The surangular (Fig. 2) is
thin and posteriorly elongated in lateral view. The
surangular, in conjunction with the angular and
articular bones, is anteroposteriorly elongated and
forms a distinctive ‘V’ shape. The anterior region of each
surangular gradually terminates near the last alveolus
of the dentary. The posterior margin of the surangular
is rounded and it bounds a small mandibular fenestra.
The angular (Fig. 2) is elongate and occupies a more
extensive area than the surangular in lateral view.
The angular is more robust than the surangular with
a strong dorsal curvature (Fig. 2) which articulates
with the retroarticular process of the articular. The
dorsal and the ventral surfaces of the angular are not
viewable in NHMUK PV R 3168. The prearticulars,
which are supposed to be present (Andrews, 1913), are
not seen.
Articular: The anterior region of the articular of
NHMUK PV R 3168 is hidden by the quadrate and
surrounding bones. The retroarticular process is,
however, extremely elongate and triangular-shaped
in dorsal view and it bears a strongly pronounced
anteroposterior keel, which separates the medial
and lateral grooves. Both grooves are concave, in
Figure 13. Atlas–axis complex (A), cervical rib (B) and proximal thoracic rib (C) of Lemmysuchus obtusidens (Andrews,
1909) comb. nov., NHMUK PV R 3168, holotype. Note there are no axial diapophyses and that the odontoid and intercen-
trum cannot clearly be distinguished. Atlas–axis complex is in lateral view, cervical rib is in ventral view, thoracic rib is in
medial view. Refer to main text for the abbreviations list. Scale bar: 5 cm.
Figure 14. Dorsal vertebra of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK PV R 3168, holotype, in
(A) anterior, (B) left lateral, (C) posterior, (D) right lateral, (E) dorsal and (F) ventral views. Refer to the main text for the
abbreviations list. Scale bar: 5 cm.
18 M. M. JOHNSON ET AL.
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particular the lateral ones. The posterior end of the
retroarticular process is slightly rounded, concave and
curves dorsolaterally. The glenoid fossa is large and
faces mediodorsally.
Splenial: All of the information on the splenial comes
from LPP.M.21. Only the anterior regions of these
bones are preserved. The splenial (Fig. 9) is situated
medially and is mediolaterally thinner in width than
Figure 15. Sacral vertebrae of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK PV R 3168, holotype, in
correct anatomical order. (A) Anterior, (B) dorsal, (C) posterior, (D) left lateral and (E) right lateral views. Refer to the main
text for the abbreviations list. Scale bar: 5 cm.
Figure 16. Scapula (A, B) and humerus (C, D) of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK PV R
3168, holotype. Scapula in (A) lateral and (B) medial views; humerus in medial (C) and lateral (D) views. Refer to the main
text for the abbreviations list. Scale bar: 5 cm.
STENEOSAURUSOBTUSIDENS 19
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the dentaries. Both splenials begin at approximately
the 15th mandibular alveoli in the dentaries. While
the coronoids are not preserved, the sulci where they
are hosted are. They participate with the mandibular
symphysis, and the anterior extension begins at
approximately the 21st alveoli of the dentaries and
continue parallel, and eventually past, the tooth row.
Dentition: As discussed above, the dentition of
NHMUK PV R 3168 is both heterodont and serrated
(with both true and false denticles; Young et al., 2015a).
The holotype has 33 isolated teeth, as well as in situ
teeth: ~29 in each dentary, 4 per premaxilla and ~29
(possibly more) per maxilla (verified by LPP.M.21).
The teeth (Fig. 12A–D) are conical, robust, single-
cusped and bicarinate, as in Machimosaurus (Martin
& Vincent, 2013; Young et al., 2015a, b; Foffa et al.,
2015; Fanti et al., 2016). They have a blunt apex in
comparison to other Steneosaurus species (Andrews,
1913). The enamel is thinner towards the base of the
crown and becomes progressively thicker towards
the apex (Fig. 12A–D), much like in Machimosaurus
(Young & Steel, 2014).
There are many protruding apicobasal enamel ridges
on these teeth, giving them a ‘wrinkled’ texture. These
apicobasal ridges are close to one another and run par-
allel from the base of the crown to approximately three
quarters of the entire tooth. At the apex, the ridges are
considerably shorter and are organized in the typical
anastomosed pattern that has been described for other
members of Machimosaurini (Young et al., 2014a,
2015a; Jouve et al., 2016). Teeth with blunter apices
are situated in the middle and posterior regions of the
tooth row and those with sharper apices are near the
anterior. The teeth have true denticles and false den-
ticles (Young et al., 2015a), although the latter cannot
be seen clearly with the naked eye. True denticles are
situated on the carina and false denticles are formed
Figure 17. Pelvis of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK PV R 3168, holotype. Ischium in
(A) medial and (B) lateral views, ilium in (C) medial and (D) lateral views and pubis in (E) medial and (F) lateral views.
Note that the acetabulum (D) is weakly concave and that the supraacetabular crest (D) is greatly reduced, and the pubic
boot (E, F) is missing. Also, the medial and lateral sides of the ilium are not completely prepared. Refer to the main text for
the abbreviations list. Scale bar: 5 cm.
20 M. M. JOHNSON ET AL.
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via interactions between the carina and enamel ridges
(Young et al., 2015a).
Postcranial skeleton: vertebral column and ribs: Most
of the vertebral column of NHMUK PV R 3168 is
preserved, so our description of vertebrae is based on
this specimen unless otherwise specified.
The first (atlas) and second (axis) vertebrae are
fused together, forming the well-developed ‘complex’
(Fig. 13A) that is common in teleosaurids (Andrews,
1913; Martin & Vincent, 2013). The axis neural arch is
not present and the odontoid and intercentrum are not
distinct from one another due to the degree of atlas–
axis fusion. The lateral surfaces of the axis are concave
and have large protruding regions for the parapophy-
ses. There are no diapophyses present behind the
odontoid process on the axis, which is slightly larger
than the atlas.
The centra of the remaining six cervical vertebrae
are amphicoelous, slightly longer in width than height,
and have sub-circular anterior and posterior articu-
lar surfaces. There is a small notch in the middle of
the dorsal margin of the centrum that is visible in
anterior view. In lateral view, the centra are slightly
spool-shaped with concave ventral margins similar
to Machimosaurus (Martin & Vincent, 2013). The
prezygapophyses are slightly anterior to the centrum
edge, with the anterior articular facets facing ventrally
and curving inwards. The postzygapophyses extend
laterally just above the base of the neural spine. The
posterior articular facets face dorsally and the trans-
verse processes are laterally wide. The neural spine is
rectangular and nearly as tall as the centrum.
Only one complete cervical rib is preserved. It is
T-shaped in dorsal view and has a distinct dorsomedial
curvature (Fig. 13B). Both the tubercular and capitu-
lar processes of this rib are rounded, and its tubercular
Figure 18. Femur of Lemmysuchus obtusidens
(Andrews, 1909) comb. nov., NHMUK PV R 3168, holotype
in (A) medial and (B) lateral views. Refer to the main text
for the abbreviations list. Scale bar: 10 cm.
Figure 19. Tibia of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK PV R 3168, holotype in (A) poste-
rior, (B) anterior and (C) lateral views. Note the anterior deflection of the proximal region. Refer to the main text for the
abbreviations list. Note the distal area of the fibula attached to the tibia. Scale bar: 5 cm.
STENEOSAURUSOBTUSIDENS 21
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is larger than the capitular. The distal area behind
the processes is short and does not extend posteriorly
while the area in front is considerably more elongated.
Fourteen robust thoracic vertebrae are preserved in
NHMUK PV R 3168 although only one is complete. The
centra (Fig. 14) are massive and appear spool-shaped
in ventral view. The articular surfaces are amphicoe-
lous and oval (slightly taller in length than wide). The
neural spine is short and broad, and not as tall as the
centrum. The transverse processes are long and wide
and are positioned approximately at the centre of the
neural arch. They are broadened anteroposteriorly,
with rounded proximal ends (Fig. 14). There is a sec-
ond projection on the transverse process, separated
from the vertebral body by a small concavity. This pro-
jection is small, circular and laterally faced.
The dorsal ribs (Fig. 13C) are dichocephalous and
have robust heads and bodies. The capitulum of
these ribs is proximodistally lengthened and dorsally
rounded (Fig. 13C) and each neck is elongated, sepa-
rating the capitulum from the tuberculum. The articu-
lar facets are flat and separated from the top of the
tuberculum. The tuberculum is a small nodule located
in the middle of the rib body. The articular facet and
tuberculum are both laterally shifted so that they are
nearly situated on the lateral edge of the body. The
costal groove is deep and runs from the ventral tuber-
culum to near the end of the rib body, disrupting an
otherwise sub-circular cross-section. The sternal end
of the rib is anteroposteriorly flat, straight and thin
in width.
There are three sacral vertebrae (Fig. 15) (Andrews,
1913). The first two are true sacral vertebrae and the
first caudal vertebra acts as a pseudo-sacral, as it looks
and functions as a third sacral. This ‘third’ sacral has
large, mediolaterally expanding transverse processes
and an expanded lateral iliac attachment area, much
like the two true sacrals. The neural spines are short
and robust and the sacral ribs curve and contact one
another (Andrews, 1913). The anterior margin of the
posterior area of the second sacral vertebra (Fig. 15B,
D) has a large, expanded projecting flange. The pres-
ence of a ‘third’ sacral vertebra is an autapomorphy
shared by L. obtusidens and Machimosaurus spp.
within Thalattosuchia (Young et al., 2014a).
Figure 20. Ankle of Lemmysuchus obtusidens (Andrews, 1909) comb. nov., NHMUK PV R 3168, holotype, including the
calcaneum (A–D), astragalus (E–G) and cuboid (H, I). Calcaneum in (A) right dorsolateral, (B) anterior, (C) left dorsolateral
and (D) posterior views; astragalus in (E) dorsal, (F) ventral and (G) posterior views; cuboid in (H) dorsal and (I) ventral
views. Scale bar: 5 cm.
Figure 21. A–C, dorsal osteoderms of Lemmysuchus
obtusidens (Andrews, 1909) comb. nov., NHMUK PV R
3168, holotype. All are in dorsal view. Note the character-
istic ornamentation pattern, with elongated pits radiating
from the centre of the keel. Refer to the main text for the
abbreviations list. Scale bar: 5 cm.
22 M. M. JOHNSON ET AL.
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Only 21 caudal vertebrae are preserved. However, it
is likely that the total caudal vertebral count is similar
to that of S. leedsi (NHMUK PV R 3806) and S. edwardsi
(NHMUK PV R 3701), of around 36–38 (Andrews,
1913) or even higher (as in S. edwardsi PETMG R275).
The caudal vertebrae become increasingly thinner and
smaller from anterior to posterior. The typical posterior
caudal vertebral centrum is thin, taller than wide and
strongly hourglass-shaped. The neural spines are thin,
tall and higher than the centrum.
Shoulder girdle and fore-limb: No coracoids are
preserved. The scapula (Fig. 16A, B) is of the typical
thalattosuchian type similar to S. leedsi (NHMUK PV
R 3806) (Andrews, 1909, 1913), being an elongate bone
with a slender body. The proximal and distal regions
extend mediolaterally, with the distal end being slightly
larger. The scapular glenoid fossa (Fig. 16B) is half-moon
shaped. The proximal region of the humerus (Fig. 16C,
D) is poorly preserved, so the deltopectoral crest and
proximal head cannot be properly described. However,
the proximal edge of the humeral head appears to be
slightly curved, as seen in other OCF teleosaurids such
as S. leedsi (NHMUK PV R 3806). The shaft of the
humerus is straight and the distal end is rounded. There
is a concave, oval (Andrews, 1913) depression in the
middle of the distal end of the humerus in lateral view
(Fig. 16D). The ulna is similar in shape to other Callovian
teleosaurids such as S. leedsi (Andrews, 1913). The
proximal region is slightly deformed and fractured. The
radius is a squat, straight bone and is unornamented.
Pelvic girdle and hind-limb: The ischium (Fig. 17A, B) is
squat and robust and only preserved in NHMUK PV R
3168. The two proximal articulation processes are divided
by a small yet deep oval notch. The smaller process has
a circular proximal head while the larger process is
posterolaterally curved. A large protruding ridge runs
proximodistally in line with the second proximal process.
Two small, sub-circular ‘bumps’, presumably for muscle
attachment, are present ~10 cm from the posterior
edge. These are not as prominent in other teleosaurids,
such as S. leedsi. The ischial blade (Fig. 17A, B) is large,
expanded and thick, with the posteroventral, sub-square
border. The anterior flange is thin and broken.
Both NHMUK PV R 3168 and PETMG R39 pre-
serve an ilium. However, in the latter specimen, it is
still articulated with the sacrum and femoral head,
is missing the anterior side and is still partially cov-
ered in matrix. Conversely, the NHMUK PV R 3168
ilia (Fig. 17C, D) are well preserved, square-shaped
and compact. The anterior-facing vertical outer rim
has a slight sub-horizontal curvature (Fig. 17C, D).
The medial attachment points of the sacral ribs are
faint (Fig. 17C) so that it is difficult to tell the ante-
rior iliac facet and posterior iliac facet apart from
one another (Fig. 17C). The acetabular depression (or
acetabular notch) is a smooth U-shaped arch in lat-
eral view (Fig. 17C) and is halfway through the ven-
tral articulating points with the pubis and ischium.
The anterior articulation facet in front of the inci-
sion is larger than that of the posterior articulation
facet and extends ventrally. The supraacetabular
crest (Fig. 17D) is poorly developed, as is the shallow
acetabulum (Fig. 17D). The preacetabular (=ante-
rior process) (Fig. 17D) is shortened (with respect to
other thalattosuchians) and well rounded and curves
laterally.
Figure 22. Comparative photographs of (A) Steneosaurus heberti (MNHN.F 1890-13), (B) Steneosaurus edwardsi (PETMG
178) and (C) Lemmysuchus obtusidens (Andrews, 1909) comb. nov., showing the dorsoposterior curvature of the ret-
roarticular process. Comparative photographs of (D) S. heberti (MNHN.F 1890-13) holotype, (E) S. edwardsi (NHMUK PV
R 2865), (F) L. obtusidens (Andrews, 1909) comb. nov., NHMUK PV R 3168, holotype and (G) Machimosaurus buffetauti
(SMNS 91415), showing the absence of antorbital fenestrae.
STENEOSAURUSOBTUSIDENS 23
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The majority of one pubis is preserved in NHMUK
PV R 3168 (Fig. 17E, F) but the pubic boot is miss-
ing. Conversely, the ventral part of the pubis is pos-
sibly preserved in matrix in PETMG 39 (PETMG R31)
(Fig. 24D). The body and distal region of the neck of the
NHMUK PV R 3168 pubis are deformed into curving
medially. The anterodistal pubic plate is expanded and
rounded along the ventral rim (Fig. 17E, F).
All the information on the hind-limb comes from
NHMK PV R 3168. The femur (Fig. 18) is slender and
long, with a weak sigmoidal curvature throughout the
shaft, which is typical of many teleosaurids (Andrews,
1909, 1913). The proximal head (Fig. 18) extends medi-
ally into the acetabulum while the anterior region of
the femoral head is ventrally curved. There is a large
concavity on the posterolateral surface of the head. The
posterior margin of the head is rugose, and this rugo-
sity continues down through the neck of the femur. In
dorsal view, the head is circular to sub-circular, with an
expanded posteromedial tuber. The ‘fourth trochanter’
(i.e. no true process, just the rugose area mentioned
before) is small compared to other Callovian teleosau-
rids and is situated on the medial neck of the femur
(Fig. 18). The two posterodistal condyles – medial
(greater) and lateral (lesser) – are clearly visible with
the medial condyle being slightly larger (Fig. 18).
The tibia (Fig. 19) is a robust bone with the proximal
end being larger than the distal end. In dorsal view,
the proximal end is heart-shaped. The tibial tuberos-
ity (Fig. 19A, C) is large and projects posterodistally.
In lateral view, it is directed ventrally at a sharply
obtuse angle (Fig. 19C). The medial side of the tibial
Figure 23. Comparative line drawings of the tibiae in posterior (left) and lateral (right) views of (A) Lemmysuchus
obtusidens holotype (NHMUK PV R 3168), (B) NHMUK PV R 3169 and (C) Steneosaurus edwardsi (PETMG R178); com-
parative line drawings of the dorsal osteoderms in dorsal view of (D) L. obtusidens holotype (NHMUK PV R 3168), (E)
NHMUK PV R 3169 and (F) S. edwardsi (PETMG R178). Refer to the main text for the abbreviations list. Scale bar: 5 cm.
24 M. M. JOHNSON ET AL.
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neck is slightly concave, while the lateral side is flat
(Andrews, 1913). The distal end is rounded, although it
is obstructed by the distal area of the fibula. The fibula
(Fig. 19) is an elongate, slender and straight bone, with
only the distal half preserved. It is slightly smaller in
width (Fig. 19A) than the tibia.
There are three ankles bones (Fig. 20): the cal-
caneum (Fig. 20A–D), astragalus (Fig. 20E–G) and
cuboid (Fig. 20H, I). They are all robust and large, with
well-developed articulation surfaces. Excluding the
clear difference in the large size, the three ankle bones
resemble those of other teleosaurids (Andrews, 1913).
All metacarpal and metatarsal fragments are slender,
as are four complete phalanges (all relatively the same
length).
Osteoderms: Fifty-six dorsal, mostly unarticulated
osteoderms are present in NHMUK PV R 3168.
Smaller osteoderms are box-shaped (Fig. 21C),
whereas larger ones are elongate and oval (Fig.
21A, B). A prominent anteroposteriorly directed
keel is present (Fig. 21A), being more pronounced
in larger osteoderms. The pits on the dorsal surface
of larger osteoderms (Fig. 21A) are oval, elongate,
deep and spaced apart. They radiate outwards
from the centre of the keel in a ‘starburst’ pattern.
The pits generally become larger further from the
centre of the osteoderms. Some pits merge with one
another along the outermost lateral margins of the
osteoderms. The ventral surfaces of all osteoderms
are smooth and unaltered.
DISCUSSION
specimens previously reFerred to
steneosaurusobtusidens
Andrews (1913) referred two large, but very incom-
plete, specimens to S. obtusidens: NHMUK PV R
3169 and NHMUK PV R 3898. The former comprises
one scapula, right coracoid, left ulna, one radius, right
ilium, femora, pubes, tibiae, a fibula, five carpal/tarsal
bones, one hyoid, three tracheal rings, five osteoderms
Figure 24. Comparative line drawings of the femora in medial view of (A) Lemmysuchus obtusidens holotype (NHMUK
PV R 3168) and Steneosaurus edwardsi [(B) NHMUK PV R 3898; (C) PETMG R178]; comparative line drawings of the ilia
in medial view of (D) L. obtusidens holotype (NHMUK PV R 3168) and S. edwardsi [(E) NHMUK PV R 3898; (F) PETMG
R178]. Refer to the main text for the abbreviations list. Scale bar: 5 cm.
STENEOSAURUSOBTUSIDENS 25
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and numerous teeth and fragmentary elements. Nine
characteristics differentiate NHMUK PV R 3169 from
L. obtusidens:
1. The tibial tuberosity is not angled as in L. obtusidens
(NHMUK PV R 3168). Instead it is directed almost
180° horizontally, similar to S. leedsi (NHMUK PV
R 3806) and S. edwardsi (NHMUK PV R 3701 and
PETMG R178) (Fig. 23A–C).
2. While the femur of NHMUK PV R 3169 is long and
gracile, somewhat similar to L. obtusidens (NHMUK
PV R 3168), it is slightly smaller in length and width
(possibly from a smaller individual; Fig. 24A–C).
3. In dorsal view, the femoral head is larger and more
triangular than that of L. obtusidens (NHMUK PV
R 3168), due to an enlarged posteromedial tuber
(Fig. 24A–C). This is somewhat similar to the con-
dition seen in the metriorhynchid Tyrannoneustes
lythrodectikos (GLAHM V1145; Young et al., 2013).
4. The greater femoral condyle of the NHMUK PV
R 3169 is much larger than the lesser condyle
(Fig. 25A–C), as opposed to L. obtusidens (NHMUK
PV R 3168) in which the greater condyle is only
slightly larger than the lesser condyle.
5. The ilium has a slender, elongate anterior process,
as opposed to the short, stubby anterior process of
L. obtusidens (NHMUK PV R 3168) (Fig. 24D–F).
6. The ilium has only two sacral rib articulation sur-
faces, and these are large and well developed. In
L. obtusidens (NHMUK PV R 3168), the ilia have
Figure 25. Four articulated vertebrae of PETMG R39, referred to Lemmysuchus obtusidens (Andrews (1909) comb.
nov., in (A) left and (B) right lateral views. Five articulated vertebrae (two dorsal, three sacral), incomplete ilium, femur
and pubis (ischium?) of PETMG R31, which is thought to correspond to PETMG R39, in (C) left and (D) right lateral views.
Scale bar: 10 cm.
26 M. M. JOHNSON ET AL.
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three poorly developed sacral rib articulation sur-
faces (Fig. 24D–F).
7. The acetabulum is deep, and the anterior-most ridge
of the ilium is vertical, whereas in L. obtusidens
(NHMUK PV R 3168), the acetabulum is poorly
concave (see Fig. 17D).
8. The anterodistal rim if the pubic plate is straighter
and sub-square, whereas in L. obtusidens (NHMUK
PV R 3168), the pubic plate rim is rounded and
circular.
9. The osteoderms of NHMUK PV R 3169 are an
enigma. Out of the five osteoderms preserved, two
have a dorsal pitting pattern similar to that of L.
obtusidens (NHMUK PV R 3168). These pits are
elongated and radiate out from the centre of the
keel. The other three are similar with those seen
in S. edwardsi (NHMUK PV R 3701 and PETMG
R178). The pits are not elongated and occur in a ran-
dom arrangement (Fig. 23D–F). Thus, we can con-
clude that NHMUK PV R 3169 is not L. obtusidens
and is morphologically more similar to S. edwardsi
(NHMUK PV R 3701) or S. leedsi (NHMUK PV R
3806).
Andrews’ (1913) second L. obtusidens referred speci-
men, NHMUK PV R 3898, consists of an ilium, ischium
and femur. All three bones are very large and robust.
However, the features in these bones differ vastly from
those seen in the L. obtusidens holotype (NHMUK
PV R 3168). The ilium of NHMUK PV R 3898 has:
(1) an elongate and slender anterior process, (2) a
pronounced supraacetabular crest and (3) a strongly
concave acetabulum (Fig. 23E; see Johnson et al.,
2015). This differs from the L. obtusidens (NHMUK
PV R 3168) ilium, which has a short anterior process,
a greatly reduced supraacetabular crest, and a shal-
low acetabulum (Fig. 25D). The ischium of NHMUK
PV R 3898 has a sub-triangular posteroventral margin
of the ischial blade (Johnson et al., 2015), as opposed
to the broad, sub-square posteroventral margin in L.
obtusidens (NHMUK PV R 3168). As Johnson et al.
(2015) showed, these morphologies exclude NHMUK
PV R 3898 from L. obtusidens and demonstrate that it
in fact pertains to S. edwardsi.
Two additional specimens from the Peterborough
Member of the OCF are here referred to as
L. obtusidens: PETMG R39 and PETMG R178. The
first specimen, PETMG R39, is a partial skull (Figs
4–6) and partial mandible (only preserving the ante-
rior end of the mandibular symphyseal region) (Fig. 7),
four articulated dorsal vertebrae (Fig. 25A, B), an oste-
oderm fragment, sacrum and some isolated bone frag-
ments (Fig. 25C, D). Parts of this specimen have been
referred to PETMG R31, another specimen that it has
been constantly mixed and stored with. However, a
specimen registration entry mentions that PETMG
R31 ‘fits with R39’. Nevertheless, the preservation
and texture of the bones and the matrix are identi-
cal in both specimens, which importantly also share
autapomorphies of L. obtusidens. Based on these lines
of evidence, we consider PETMG R39 and PETMG
R31 belonging to the same individual and both per-
tain to L. obtusidens. The skull of PETMG R39 (Figs
4–6) includes the nasals, posterior maxillae, jugal and
anterior orbit. Several alveoli are visible on both lat-
eral sides of the maxillae. The alveoli are separated by
variable interalveolar spaces (always fewer than one
alveolus length but longer than half) and most teeth
are still in situ. Two erupting teeth show the typical
Machimosaurini crown ornamentation. This specimen
is referable to L. obtusidens due to the following fea-
tures: (1) closure of the antorbital fenestrae; (2) there
is a slight beginning of a ‘dome’ near the posterior sec-
tion of the nasals; (3) the teeth have blunt apices, den-
ticles and the characteristic Machimosaurini enamel
ornamentation pattern and (4) an extreme anteropos-
terior elongation of the jugal.
PETMG R31 consists of five articulated vertebrae
(two complete dorsal, two complete and one incom-
plete sacral), incomplete ilium, femur and pubis (or
ischium?) (Fig. 25C, D). The sacral vertebrae largely
resemble the L. obtusidens holotype (NHMUK PV R
3168). Although the posterior-most vertebra is incom-
plete, one of its ribs is partially preserved, and there is
little doubt that it is a sacral rib due to its shape and
dimension, with an expanded flange. The fragmentary
status of the specimen and abundant matrix around
the bones does not allow direct comparison of other ele-
ments. Thus, PETMG R31 pertains to Lemmysuchus
based on the presence of three sacral vertebrae, and
the fact that it likely belongs with PETMG R39.
The second specimen, PETMG R178, represents a
nearly complete skeleton. However, it lacks charac-
teristics seen in the L. obtusidens holotype (NHMUK
PV R 3168). The dorsal rim of larger cervical ribs
does not curve dorsomedially. The shape and posi-
tion of the tuberculum in the dorsal ribs is similar
to S. edwardsi (NHMUK PV R 3701), whereas L.
obtusidens (NHMUK PV R 3168) displays a more
medial position of the tuberculum. The ilium has a
deep well-developed acetabulum and an elongate,
slender anterior process, which differs from the
shallow acetabulum and the proportionally shorter
anterior process seen in L. obtusidens (NHMUK
PV R 3168) (Fig. 24D, E). The ischium is gracile
and the posteroventral margin of the ischial blade
is sub-triangular in shape, which differs from the
robust ischium with a square-shaped posteroventral
ischial blade of L. obtusidens (NHMUK PV R 3168).
The proximal tibia is not strongly deflected anteri-
orly as in L. obtusidens (NHMUK PV R 3168) and
Machimosaurus (Hua, 1999). The skull of PETMG
STENEOSAURUSOBTUSIDENS 27
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
R178 lacks the strongly convex (‘domed’) nasals seen
in L. obtusidens (NHMUK PV R 3168 and PETMG
R39), although this may be due to preservation. The
dorsal osteoderm ornamentation differs from that
seen in L. obtusidens (NHMUK PV R 3168). The
pitting pattern is random, as seen in S. edwardsi
(NHMUK PV R 3701). Thus, PETMG R178 is not ref-
erable to L. obtusidens and is more morphologically
similar to S. edwardsi.
Hua et al. (1994) described a fragmentary skeleton
from the upper Callovian of Villers-sur-Mer, Calvados,
France, and referred it to S.obtusidens. It was the
first non-English specimen referred to L. obtusidens.
However, comparing the figures from Hua et al. (1994)
with the L. obtusidens holotype (NHMUK PV R
3168) shows that the ischium, ilium and dorsal osteo-
derms do not match. In the French specimen, the ilium
anterior process is much more elongated and slender
than that seen in the Lemmysuchus holotype (NHMUK
PV R 3168). The supraacetabular crest is pronounced,
the acetabular depression is strongly concave and the
posterior margin of the ischial blade is sub-triangu-
lar. The osteoderm (Hua et al., 1994; fig. 1a) lacks the
‘starburst’ pattern of pits. As with PETMG R178, this
specimen more closely resembles S. edwardsi than L.
obtusidens.
Foffa et al. (2015) described an incomplete mandi-
ble (DORCM G3939), which preserves the symphyseal
region up to approximately the 19th alveoli (alveoli
one and two are missing). Due to the incomplete-
ness of its preservation, the lower jaw could not be
confidently assigned to a taxon but was referred to
S. cf. obtusidens. It is difficult to determine for cer-
tainty whether DORCM G3939 is L. obtusidens, as so
little of it is preserved; however, the high symphyseal
tooth count, the Meckelian groove not being exposed
on the dorsal surface of the splenials, the blunt tooth
apices, the anastomosed apical enamel ornamentation,
presence of denticles and deep reception pits place it
within Machimosaurini. If this specimen does belong
to L. obtusidens, it expands the stratigraphic range of
this taxon into the early Oxfordian.
comparison witH otHer ocF teleosaurids
Lemmysuchus obtusidens (NHMUK PV R 3168,
PETMG R39) has numerous teleosaurid apomorphies
including: a laterally expanded premaxilla and ante-
rior dentary, and a relatively small frontal (Andrews,
1913). However, L. obtusidens has a number of auta-
pomorphies, particularly in the postcranial skeleton
(Tables 1 and 2).
Andrews (1913) recognized some of these autapo-
morphies: (1) three sacral vertebrae; (2) blunt, heavily
ornamented teeth and (3) a unique osteoderm pat-
tern (however, points 1 and 2 are now recognized as
characters shared with Machimosaurus, see Diagnosis
and Discussion; Young et al., 2014a, 2015a; Jouve
et al., 2016). While Andrews (1913) gave a generally
good description of the skull, we disagree with some
of his observations regarding the antorbital fenestrae,
lacrimal and sacral vertebrae. These autapomorphies
Table 1. Comparison of cranial characters between Lemmysuchus obtusidens and selected specimens of other
teleosaurids
Characteristics Lemmysuchus
obtusidens
Machimosaurus
buffetauti
Steneosaurus
heberti
Steneosaurus
edwardsi
Steneosaurus
leedsi
NHMUK PV R 3168 SMNS 91415,
Martin & Vincent
(2013), Young et al.
(2014a)
MNHN.F 1890-13 MNHN.F RJN 118,
NHMUK PV R
3701, PETMG R178
NHMUK PV R
3806
PETMG R39 (+
PETMG R31)
LPP.M.21
Antorbital
fenestrae
Absent Absent Absent Absent Present
Nasal dorsal
surface
Strongly convex Slightly convex Slightly convex Slightly convex Slightly convex
Frontal
ornamentation
Yes: large circular
pits
Yes: well-developed
pits/ridges
Yes: ridges Yes: circular pits Yes: ridges
Supratemporal
fenestra
shape
Rectangular (anter-
oposteriorly
elongated)
Rectangular
(anteroposteri-
orly elongated)
Parallelogram
(slightly anter-
oposteriorly
elongated)
Parallelogram
(slightly anter-
oposteriorly
elongated)
Parallelogram
(slightly anter-
oposteriorly
elongated)
Occipital
tuberosities
Yes: pronounced Yes: pronounced Yes: pronounced No No
Nuchal crest Pronounced Reduced Reduced Small Small
28 M. M. JOHNSON ET AL.
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
readily distinguish it from two common OCF teleosau-
rids, S. leedsi and S. edwardsi.
The skull of L. obtusidens (NHMUK PV R 3168) is
marked similar to Machimosaurus (Table 1; see Krebs,
1967; Buffetaut, 1982a; Martin & Vincent, 2013;
Young et al., 2014a; Fanti et al., 2016) in being large
and robust. This is opposite of S. leedsi (NHMUK
PV R 3806), which has a slender skull. Steneosaurus
edwardsi (NHMUK PV R 3701, PETMG R178) has a
large skull similar to L. obtusidens (NHMUK PV R
3168), with some specimens of S. edwardsi being even
larger than the L. obtusidens holotype. Both S. leedsi
(NHMUK PV R 3806) and S. edwardsi (NHMUK PV
R 3701) lack the dorsoventrally deep ‘domed’ nasals-
frontal as seen in L. obtusidens (NHMUK PV R 3168).
The supratemporal fossae in L. obtusidens (NHMUK
PV R 3168) extend further anteriorly along the frontal
than those of S. leedsi (NHMUK PV R 3806) and S.
edwardsi (NHMUK PV R 3701). The articular, suran-
gular and angular bones of L. obtusidens (NHMUK
PV R 3168) are more elongated anteroposteriorly than
lateromedially, giving them a combined ‘V’ shape. This
differs in comparison to S. edwardsi (NHMUK PV
R3 701), in which the three bones are not elongated
anteroposteriorly. Steneosaurus leedsi (NHMUK PV
R 3806) displays the same shape and anteroposterior
elongation as L. obtusidens (NHMUK PV R 3168),
although it is smaller and slenderer. The Meckelian
groove is not excavated on the dorsal surface of the
symphyseal splenial in L. obtusidens (NHMUK PV R
3168) (Fig. 26E), which it shares with M. mosae neotype
(Fig. 26F), S. edwardsi (NHMUK PV R 3701) (Fig. 26C)
and S. hulkei (NHMUK PV R 2074) (Fig. 26D). Other
thalattosuchians, such as S. leedsi (NHM UK PV R
3806, NHMUK PV R 3320) (Fig. 26A, B), have the
Meckelian groove deeply excavated on the dorsal sur-
face of the splenial. As mentioned before, L. obtusidens
(PETMG R39) lacks any evidence of antorbital
fenestrae (contra Andrews, 1913), the condition shared
with S. edwardsi (PETMG R178), Machimosaurus,
and S. heberti (MNHN.F 1890-13). Small, slit-like
fenestrae are present in S. leedsi (NHMUKPV R 3806).
The teeth of S. edwardsi (NHMUK PV R 3701) and S.
leedsi (NHMUK PV R 3806) are more elongate and
slender than those of L. obtusidens (NHMUK PV R
3168) and have pointed apices continuously through-
out the maxillae and dentaries, as well as lacking an
anastomosed apical pattern.
Table 2. Comparison of postcranial characters between Lemmysuchus obtusidens and selected specimens of other
teleosaurids
Characteristics Lemmysuchus
obtusidens
Machimosaurus
buffetauti and
M. mosae,
Young et al. (2014a)
Steneosaurus
heberti
Steneosaurus
edwardsi
Steneosaurus
leedsi
NHMUK PV R
3168
MNHN.F 1890-13 NHMUK PV R
3701
NHMUK PV R
3806
PETMG R39
(PETMG R31)
PETMG R178
Ilium Short anterior
process; shallow
acetabulum; faint
supraacetabular
crest
Long anterior
process; deep
acetabulum;
well-developed
supraacetabular
crest
Long anterior
process; deep
acetabulum;
well-developed
supraacetabular
crest
Long slender
process, deep
acetabulum;
well-developed
supraacetabular
crest
Long anterior
process; deep
acetabulum;
well-developed
supraacetabular
crest
Ischium Broad ischial blade;
sub-square poster-
oventral margin
Somewhat broad
ischial blade; sub-
square poster-
oventral margin
Slender ischial
blade; sub-trian-
gular posteroven-
tral margin
Slender ischial
blade; sub-trian-
gular posteroven-
tral margin
Slender ischial
blade; sub-tri-
angular poster-
oventral margin
Number of sacral
vertebrae
3 (2 true,
1 pseudo)
3 2 2 2
Femur Sub-triangular head
(dorsal view);
medial condyle
slightly larger than
lateral condyle;
sigmoidal
Triangular head
(dorsal view);
medial condyle
larger than
lateral condyle;
sigmoidal
Triangular head
(dorsal view);
medial condyle
larger than
lateral condyle;
slightly sigmoidal
Triangular to
‘kidney-bean’
shaped head
(dorsal view);
medial condyle
much larger than
lateral condyle;
slightly sigmoidal
Triangular head
(dorsal view);
medial condyle
much larger than
lateral condyle;
sigmoidal
Tibial tuberosity Sharply angled Sharply angled Horizontal Horizontal Horizontal
STENEOSAURUSOBTUSIDENS 29
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
Aside from the osteoderms and sacral vertebrae,
Andrews (1913) largely neglected to describe the post-
cranial skeleton. Herein, we have shown the postcra-
nia of L. obtusidens to be distinctive (Table 2). One
striking difference found in L. obtusidens (NHMUK
PV R 3168) is the absence of axial diapophyses.
These processes are present in S. leedsi (NHMUK
PV R 3806) and S. edwardsi (NHMUK PV R 3701).
Steneosaurus bollensis, however, also lacks the axial
diapophyses (see Westphal, 1962).
The two primordial sacrals in L. obtusidens
(NHMUK PV R 3168) are similar in form to S. leedsi
(NMHUK PV R 3806) and S. edwardsi (NHMUK
PV R 3701) (Andrews, 1913). The anterior project-
ing flange on the second sacral vertebra is seen in
S. leedsi (NHMUK PV R 3806), although it is much
smaller and does not extend anteriorly (Fig. 27B) as
in L. obtusidens (NHMUK PV R 3168) (Fig. 27A).
The cervical rib of L. obtusidens (NHMUK PV R
3168) (Fig. 28A) has a distinct medial curvature
in the dorsal rim. The cervical ribs of S. edwardsi
(NHMUK PV R 3701) and S. leedsi (NHMUK PV
R 3806) both have straight, T-shaped dorsal rims
(Fig. 28B–D). The area posterior to the tubercular
and capitular processes of the cervical rib is also
shorter than the anterior area in L. obtusidens
(NHMUK PV R 3168), whereas in S. edwardsi
(NHMUK PV R 3701) and S. leedsi (NHMUK PV
R 3806), they are more elongated (Fig. 28) and are
approximately the same length.
Figure 26. Comparative photographs of Steneosaurus leedsi (A) NHMUK PV R 3806; (B) NHMUK PV R 3220, (C)
Steneosaurus edwardsi (NHMUK PV R 3701), (D) Steneosaurus hulkei (NHMUK PV R 2074), (E) Lemmysuchus
obtusidens (Andrews, 1909) comb. nov., NHMUK PV R 3168) and (F) Machimosaurus mosae (taken from Young et al.
2014a, fig. 19), showing the shallow vs. deep excavation of the Meckelian groove. Note that (A–B) are much more deeply
excavated and exposed than (C–F). Scale bar: 10 cm.
Figure 27. Comparative line drawings of (A) Lemmysuchus obtusidens holotype (NHMUK PV R 3168) and (B) Steneosaurus
leedsi (NHMUK PV R 3806) articulated sacral vertebrae. Note that the anterior projecting flange on the second sacral verte-
bra in S. leedsi (B) does not extend anteriorly and is small. Refer to the main text for the abbreviations list. Scale bar: 5 cm.
30 M. M. JOHNSON ET AL.
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
There are three features seen in the dorsal ribs of
L. obtusidens (NHMUK PV R 3168) in conjunction
with S. edwardsi (NHMUK PV R 3701) and S. leedsi
(NHMUK PV R 3806) (Fig. 29):
1. Both the tuberculum and articular facet are shifted
onto the medial edge of the rib in L. obtusidens
(NHMUK PV R 3168), as described before. The
position of these articular surfaces in L. obtusidens
(NHMUK PV R 3168) could be due to either the
massive size of the ribs causing the tuberculum to
shift medially or are solely due to deformation. In
S. leedsi (NHMUK PV R 3806), the tuberculum and
articular surface are situated directly in the middle
of the rib and are small. In S. edwardsi (NHMUK
PV R 3701), the tuberculum is also situated medi-
ally, but closer to the lateromedial edge of the rib.
2. The proximal head of the ribs in L. obtusidens
(NHMUK PV R 3168) and S. edwardsi (NHMUK
PV R 3701) are elongated proximodistally and are
rectangular in dorsal view. In medial view, the dor-
sal edges of the two specimens appear curved. In S.
leedsi (NHMUK PV R 3806), the rib head is as long
as it is wide. It is flat and circular in dorsal view
and straight in medial view.
3. The sternal rib end is flat in L. obtusidens (NHMUK
PV R 3168) and S. edwardsi (NHMUK PV R 3701),
while in S. leedsi (NHMUK PV R 3806), it is more
rounded, similar to metriorhynchids (Wilkinson et
al., 2008).
There is also a combination of six pelvic and hind-limb
characteristics that readily distinguishes L. obtusidens
from S. leedsi and S. edwardsi (Table 2). These charac-
teristics were not noted by Andrews (1909, 1913) and
are here listed for the first time:
1. The iliac anterior process in L. obtusidens is short
and squat, as opposed to the elongate, slightly thin-
ner processes S. leedsi (NHMUK PV R 3806) and S.
edwardsi (NHMUK PV R 3701) (Andrews, 1913).
2. The poorly developed sacral rib attachment areas
and acetabulum of L. obtusidens (NHMUK PV
R 3168) differs from S. edwardsi (NHMUK PV R
3701) and S. leedsi (NHMUK PV R 3806) in that in
L. obtusidens, they are both poorly developed (pos-
sibly due to preservation).
3. The posteroventral margin of the ischial plate in
L. obtusidens (NHMUK PV R 3168) is sub-square
in shape, and is not as blunt or widened as seen
in metriorhynchids (e.g. Wilkinson et al., 2008), but
is broader than the sub-triangular posterior mar-
gin seen in S. leedsi (NHMUK PV R 3806) and S.
edwardsi (NHMUK PV R 3701) (Andrews, 1913).
4. The anterodistal rim of the pubic plate is curved in
a circular fashion, much like that seen in S. leedsi
(NHMUK PV R 3806). This differs from S. edwardsi
(NHMUK PV R 3701), in that the anterodistal pubic
plate rim is straight and square-like with a sharp
anterodistal edge.
5. The sigmoidal curvature of the L. obtusidens
(NHMUK PV R 3168) femur is most similar to
S. leedsi (NHMUK PV R 3806) in being weak. In
S. edwardsi (NHMUK PV R 3701, NHMUK PV
R 3898), the curvature throughout the femur is
strongly pronounced (Johnson et al., 2015).
6. In L. obtusidens (NHMUK PV R 3168), there is a
distinctive sharply angled tibial tuberosity that
is shared with Machimosaurus (Hua, 1999). In
S. leedsi (NHMUK PV R 3806) and S. edwardsi
(NHMUK PV R 3701), the tibial tuberosity is hori-
zontal and shows no angle.
Figure 28. Comparative line drawings of (A) Lemmysuchus
obtusidens holotype (NHMUK PV R 3168), (B) Steneosaurus
leedsi (NHMUK PV R 3806) and (C) Steneosaurus edwardsi
(NHMUK PV R 3701); (D) PETMG R178, cervical ribs.
Scale bar: 5 cm.
STENEOSAURUSOBTUSIDENS 31
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
The dorsal surface ‘starburst’ osteoderm ornamenta-
tion of L. obtusidens (NHMUK PV R 3168) differs from
the ornamentations seen in S. edwardsi (NHMUK PV
R 3701) and S. leedsi (NHMUK PV R 3806) (Fig. 23D–
F). In S. edwardsi (NHMUK PV R 3701 and PETMG
R178), the majority of pits are circular in shape and
are not as deep as L. obtusidens (NHMUK PV R 3168).
The pits are closely packed together and are distrib-
uted in a random pattern, as opposed to the ‘star-
burst’ pattern in L. obtusidens (NHMUK PV R 3168).
In S. leedsi (NHMUK PV R 3806), the majority of
the pits are circular, with some being oval in shape.
The pits radiate outwards in a sub-circular fashion
and are closely packed together, which differs from L.
obtusidens (NMHUK PV R 3168).
Andrews (1909, 1913) described the postcranial
material (not including the dorsal osteoderms) of L.
obtusidens as so similar ‘to that of S. durobrivensis
[that] special description is unnecessary.’ However,
here we have shown that not only is the postcrania
of L. obtusidens distinct, but there were at least two
different postcranial morphotypes among OCF tele-
osaurids. A robust, stockier morphotype was repre-
sented by Lemmysuchus (i.e. stout ilia and tibiae,
broad ischial blade, large centra and three sacral ver-
tebrae), and a slenderer morphotype was represented
by S. leedsi and S. edwardsi (with a gracile ilia, tibiae,
and ischial blade, smaller centra, and two sacral verte-
brae). These differences may reflect habitat partition-
ing among sympatric teleosaurids, with L. obtusidens
suggested as being more terrestrial, and/or living in
higher energy environments.
body lengtH
The basicranial length of the L. obtusidens holotype
(NHMUK PV R 3168) is ~1.16 m. The vertebral col-
umn is not completely preserved. There is one dorsal
and one cervical vertebra missing, and the majority
of the caudal region is missing. Using the Young et al.
(2016b), basicranial length vs. body length equations
yields a total body length estimate of between 556.995
and 558.173 cm. Using the femoral length vs. body
length equations yields a total body length estimate
of between 575.742 ad 582.3 cm. Young et al. (2016b)
found femoral-based estimates to be the more reliable
than cranial-based estimates, thus a body length of
~5.8 m seems likely for L. obtusidens.
Figure 29. Comparative line drawings of (A) Lemmysuchus obtusidens holotype (NHMUK PV R 3168), (B) Steneosaurus
leedsi (NHMUK PV R 3806) and (C) Steneosaurus edwardsi (NHMUK PV R 3701) dorsal ribs. Refer to the main text for the
abbreviations list. Scale bar: 5 cm.
32 M. M. JOHNSON ET AL.
© 2017 The Linnean Society of London, Zoological Journal of the Linnean Society, 2017, XX, 1–34
Lemmysuchus obtusidens has long been considered to
be the largest teleosaurid in the OCF (see Andrews, 1913;
Young et al., 2015a). However, as noted above, the largest
specimen previously referred to L. obtusidens (NHMUK
PV R 3898) has recently been re-assigned to S. edwardsi
(Johnson et al., 2015). Young et al. (2016b) found NHMUK
PV R 3898 to be between 659.51 and 666.66 cm using the
femoral-based equations. Thus, S. edwardsi is the largest
known crocodylomorph of the Middle Jurassic.
CONCLUSIONS
Here, we re-describe the holotype of S.obtusidens
(NHMUK PV R 3168), demonstrate that it is indeed
a valid species and establish a new monotypic genus,
Lemmysuchus, for the taxon. It has five autapo-
morphies and shares nine synapomorphies with
Machimosaurus, thus supporting Machimosaurini
(Lemmysuchus + Machimosaurus) (Young et al., 2015b;
Jouve et al., 2016). This suite of characteristics falsifies
the hypothesis that L. obtusidens is a subjective jun-
ior synonym of S. edwardsi. Additionally, L. obtusidens
lacks eight of the Machimosaurus autapomorphies
(including three premaxillary alveoli, a considerably
smaller medial hemicondyle and variable presence of
carinae) listed by Young et al. (2014a), thus falsifying
the hypothesis that L. obtusidens is a subjective junior
synonym of M. hugii. Moreover, most specimens previ-
ously referred to L. obtusidens are herein considered
to pertain to other taxa. We conclude that only three
specimens can reliably be referred to L. obtusidens: a
nearly complete skull (LPP.M.21) from the E. corona-
tum ammonite Zone of Migné-les-Lourdines, France;
an incomplete skull with associated postcranial ele-
ments from the OCF of England (PETMG R39) and a
partial rostrum thought to be from the OCF (NOTNH
FS3361). As such, L. obtusidens was a somewhat rare
taxon in the Callovian of Europe, currently known
only from England and France. This contrasts with its
sister taxon Machimosaurus, which was widespread
and common in European and Tethys shallow marine
and brackish ecosystems during the Late Jurassic.
ACKNOWLEDGEMENTS
We thank G. Wass (PETMG), P. Tomlinson (DORCM)
and M. Riley (CAMSM) for access to collections
and their much appreciated assistance and advice;
G. Garcia for photographs of LPP.M.21; P. Hurst
and K. Webb (NHMUK Image Resources) for pho-
tography of the Lemmysuchus obtusidens holotype
(NHMUK PV R 3168) and R. Holmes and J. Liston
for advice and guidance. MTY received support for
his visits to France (FR-TAF-4021) and Germany
(DE-TAF-5132) from the SYNTHESYS Project,
which is financed by the European Community
Research Infrastructure Action, under the
FP7 ‘Capacities’ Program. He would like to thank
R. Allain (MNHN), R. Schoch (SMNS), D. Vasilyan
and M. Rabi (GPIT) for collections access and host-
ing during these trips.
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... It is worth noting that some teleosauroids, such as the machimosaurins Lemmysuchus obtusidens (Andrews, 1909), Machimosaurus spp., and Yvridiosuchus boutilieri (Eudes-Deslongchamps 1868a), show teeth similar in certain features of their crown ornamentation to those of MZ VIII Vr-72 as well (Young et al. 2014;Johnson et al. 2018Johnson et al. , 2020. Specifically, as in MZ VIII Vr-72, the tooth crowns of the machimosaurins show ridged basal halves of the crowns that gradually change into a vermicular pattern at the apex. ...
... The apical region of the crown lacks the conspicuous anastomosed pattern that is observable in Machimosaurus spp. (Young et al. 2014) and the apicobasal ridges ("pronounced vertical striae" of Tyborowski and Błażejowski 2019a) are very wide, separated by a somewhat vermicular surface ("numerous wrinkles" of Tyborowski and Błażejowski 2019a), and appear to be of a much higher relief than in machimosaurins (Johnson et al. 2018(Johnson et al. , 2020. ...
... Such categories, however, are too vague to be of any value, especially when ignoring their temporal settings (the Boreal assemblages discussed by Tyborowski and Błażejowski 2019a are Volgian [Tithonian-earliest Berriasian], and the Mediterranean and "Matyja-Wierzbowski Line" faunas fall within partly overlapping intervals of Kimmeridgian and Tithonian) and the complex evolutionary history of marine reptile clades during the Middle and Late Jurassic. For example, placing thalattosuchians collectively in a "crocodylomorph bin" significantly oversimplifies their Middle and Late Jurassic dispersal patterns and diverse ecological adaptations (see Young et al. 2013aYoung et al. , b, 2014Foffa et al. 2015Foffa et al. , 2018aFoffa et al. -c, 2019Stubbs and Benton 2016;Johnson et al. 2018Johnson et al. , 2020. With respect to plesiosaurs, in turn, pliosaurids clearly occurred south of the "line" in the Kimmeridgian (Bardet et al. 1993). ...
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Marine reptiles from the Upper Jurassic of Central Europe are rare and often fragmentary, which hinders their precise taxonomic identification and their placement in a palaeobiogeographic context. Recent fieldwork in the Kimmeridgian of Krzyżanowice, Poland, a locality known from turtle remains originally discovered in the 1960s, has reportedly provided additional fossils thought to indicate the presence of a more diverse marine reptile assemblage, including giant pliosaurids, plesiosauroids, and thalattosuchians. Based on its taxonomic composition, the marine tetrapod fauna from Krzyżanowice was argued to represent part of the “Matyja-Wierzbowski Line”—a newly proposed palaeobiogeographic belt comprising faunal components transitional between those of the Boreal and Mediterranean marine provinces. Here, we provide a detailed re-description of the marine reptile material from Krzyżanowice and reassess its taxonomy. The turtle remains are proposed to represent a “plesiochelyid” thalassochelydian (Craspedochelys? sp.) and the plesiosauroid vertebral centrum likely belongs to a cryptoclidid. However, qualitative assessment and quantitative analysis of the jaws originally referred to the colossal pliosaurid Pliosaurus clearly demonstrate a metriorhynchid thalattosuchian affinity. Furthermore, these metriorhynchid jaws were likely found at a different, currently indeterminate, locality. A tooth crown previously identified as belonging to the thalattosuchian Machimosaurus is here considered to represent an indeterminate vertebrate. The revised taxonomy of the marine reptiles from Krzyżanowice, as well as the uncertain provenance of the metriorhynchid specimen reported from the locality, cast doubt on the palaeobiogeographic significance of the assemblage.