Dentary Fragment Research Articles

Skull of a new periptychid mammal from the lower Paleocene Denver Formation of Colorado (Corral Bluffs, El Paso County)

The Periptychidae, an extinct group of archaic ungulates (‘condylarths’), were the most speciose eutherian mammals in the earliest Paleocene of North America, epitomizing mammalian ascendency after the Cretaceous–Paleogene (K–Pg) mass extinction. Although periptychids are mostly known from fragmentary gnathic remains, the Corral Bluffs area within the Denver Basin, Colorado, has yielded numerous exceptionally well-preserved mammalian fossils, including periptychids, from the earliest Paleocene. Here we describe a partial cranium and articulated dentaries plus an additional unassociated dentary fragment of a small-bodied (~273–455 g) periptychid from ca. 610 thousand years after the K–Pg mass extinction (Puercan 2 North American Land Mammal ‘age’) at Corral Bluffs. Based on these new fossils we erect Militocodon lydae gen. et sp. nov. The dentition of M. lydae exhibits synapomorphies that diagnose the Conacodontinae, but it is plesiomorphic relative to Oxyacodon, resembling putatively basal periptychids like Mimatuta and Maiorana in several dental traits. As such, we interpret M. lydae as a basal conacodontine. Its skull anatomy does not reveal clear periptychid synapomorphies and instead resembles that of arctocyonids and other primitive eutherians. M. lydae falls along a dental morphocline from basal periptychids to derived conacodontines, which we hypothesize reflects a progressive, novel modification of the hypocone to enhance orthal shearing and crushing rather than grinding mastication. The discovery and thorough descriptions and comparisons of the partial M. lydae skull represent an important step toward unraveling the complex evolutionary history of periptychid mammals.

A Skink (Squamata: Scincidae) from the Late Miocene of Ukraine

Maxillary and dentary fragments of cf. Plestiodon (Squamata: Scincidae) are described from the Late Miocene of the Gritsev locality, Ukraine. This first, although tentative, fossil record of the genus adds new data to the fossil history of European Cenozoic skinks.

A NEW SPECIES OF <i>HAPALODECTES</i> (HAPALODECTIDAE, MESONYCHIA) FROM THE PALEOCENE OF MONGOLIA

Hapalodectes paradux sp. nov. (Hapalodectidae, Mesonychia) is described on the base of the dentary fragment with М2–М3 from the Tsagan-Khushu locality in Mongolia (Upper Paleocene, Naran Bulak Formation, Zhigden Member). The M2 and M3 are approximately the same size, with a high protoconid, anteriorly displaced reduced metaconid, anterolingually directed protocristid, very deep posterior notch, narrow talonid, and distinct hypoconid, entoconid and hypoconulid. Based on dental characters, the new species is presumably related to the base of the lineage of Hapalodectes that dispersed to North America at the beginning of the Eocene. Tsagan-Khushu is the only known locality where two species of Hapalodectes co-occur (larger H. dux Lopatin, 2001 and smaller H. paradux sp. nov.).

A New Species of Hapalodectes (Hapalodectidae, Mesonychia) from the Paleocene of Mongolia

Hapalodectes paradux sp. nov. (Hapalodectidae, Mesonychia) is described on the base of the dentary fragment with M2–M3 from the Tsagan-Khushu locality in Mongolia (Upper Paleocene, Naran Bulak Formation, Zhigden Member). The M2 and M3 are approximately the same size, with a high protoconid, anteriorly displaced reduced metaconid, anterolingually directed protocristid, very deep posterior notch, narrow talonid, and distinct hypoconid, entoconid and hypoconulid. Based on dental characters, the new species is presumably related to the base of the lineage of Hapalodectes that dispersed to North America at the beginning of the Eocene. Tsagan-Khushu is the only known locality where two species of Hapalodectes co-occur (larger H. dux Lopatin, 2001 and smaller H. paradux sp. nov.).

A peirosaurid mandible from the Albian–Cenomanian (Lower Cretaceous) of Algeria and the taxonomic content of Hamadasuchus (Crocodylomorpha, Peirosauridae)

AbstractPeirosaurids form an extinct clade of terrestrial crocodylomorphs from the Cretaceous of Africa and South America. Here, we describe a new mandibular ramus attributable to Hamadasuchus cf. rebouli from the Albian–Cenomanian of La Gara Samani (Algeria). We propose an emended diagnosis for this taxon, originally described from a left dentary fragment from the Kem Kem Group of Morocco and discuss the assignment of the specimens currently referred to it. Using ontogenetic series of extant crocodylians, we show that several mandibular characters commonly used to differentiate between close taxa instead record intraspecific or ontogenetic variability. In contrast, reliable mandibular characters enable us to propose that the current taxonomic content of Hamadasuchus rebouli should be reduced to three specimens, pending future description of relatable cranial remains. Finally, we demonstrate the importance of mandibular characters in phylogenies, by recovering the new specimen from La Gara Samani as closely related to North African peirosaurids on the basis of a data matrix designed solely on mandibular characters.

Unraveling the taxonomy of the South African mosasaurids

Until recently, only one mosasaur was identified in South Africa based on disarticulated skull bones including two dentary fragments and a frontal with articulated elements. These were discovered in 1901 in Pondoland, Eastern Cape and were initially described by Broom in 1912 when he assigned them to Tylosaurus capensis. Aside from this specimen, two other mosasaur remains are known but have remained undescribed and include an isolated muzzle unit and an isolated vertebra. The current study provides a morphological description and taxonomic interpretation of all the mosasaur remains discovered in South Africa. It is suggested that the specimen originally assigned to Tylosaurus is a mosaic of two taxa: A dentary fragment and frontoparietal show affinities with Prognathodon, while a second dentary fragment shows features similar to those of Taniwhasaurus. The muzzle unit presents Prognathodon-like features, and a more recently discovered incomplete vertebra is referred to as an indeterminate Plioplatecarpine. We therefore recognize at least three mosasaur taxa from the Late Cretaceous deposits of South Africa, which we tentatively refer to cf. Prognathodon, cf. Taniwhasaurus, and cf. Plioplatecarpinae. A shark tooth that was embedded in the matrix around the Prognathodon muzzle unit was identified as a Squalicorax pristodontus (Late Campanian to Late Maastrichtian). Strontium analysis of the mosasaur tooth enamel from the same muzzle unit of the cf. Prognathodon material was dated to Late Maastrichtian (87Sr/86Sr = 0.707817; age = 66.85Ma).

A reappraisal of Jeddaherdan aleadonta (Squamata: Acrodonta), the purported oldest iguanian lizard from Africa

Jeddaherdan aleadonta Apesteguía et al., 2016 is currently known as the first and single Mesozoic iguanian lizard from Africa. The original description and age of the holotype and only known specimen (i.e. a dentary fragment bearing five teeth) are revised here. We show that this fragmentary specimen was misinterpreted anatomically, does not come from Cretaceous beds but is instead Quaternary in age, and must be assigned to an indeterminate species of Uromastyx (spiny-tailed lizards). Therefore, the genus Jeddaherdan is considered a junior synonym of Uromastyx, and the species J. aleadonta (= Uromastyx sp.) is considered a nomen dubium. Our results refute the presence of iguanian lizards in the Mesozoic of Africa and have major implications for reconstructing the evolution and palaeobiogeography of this group.

A new SANU (Mammalia, Panperissodactyla) from the early Eocene levels of the Lumbrera Formation at Los Cardones National Park (Salta Province, Northwestern Argentina)

ABSTRACT New remain of a SANU from the lower levels of the Lumbrera Formation is described. It consists of a left dentary fragment with a m3 preserving a partially broken trigonid and a complete talonid. Kyraodus churcalensis gen. et. sp nov. is characterised by the following combination of features: brachydont and bunodont molar; talonid larger than trigonid; distal wall of the metaconid not inflated; hypoconid subequal in height, but more voluminous than the distally placed hypoconulid; small entoconid closer to the hypoconulid; metastylid vestigial; strong cristid obliqua lingually projected and mesially ascending, closing labially the talonid basin, which is a narrow oblique valley labio-lingually opened; hypocristid present without contacting the hypoconulid; postcristid present, contacting the entoconid and closing the small valley between the later and hypoconulid; strong mesio-labial cingulid and reduced disto-labial one. The cladistic analysis performed yields 380 most parsimonious trees (177 steps each). In the strict consensus, Kyraodus is positioned in a clade with Mioclaenidae, Litopterna, Didolodontidae and Phenacodontidae, separated from Notoungulata plus Kollpaniidae. Kyraodus represents the ancient condylarth known from Northwestern Argentina and the accompanying fauna is the first confirmed early Ypresian assemblage of Argentina highlighting the importance of the region for the early radiation of native ungulates. urn:lsid:zoobank.org:act:55379E92-AB62-4E9A-9FC8-2F1B6A1B2B39

Sauropod dinosaur teeth from the lower Upper Cretaceous Winton Formation of Queensland, Australia and the global record of early titanosauriforms.

The Upper Cretaceous Winton Formation of Queensland, Australia, has produced several partial sauropod skeletons, but cranial remains—including teeth—remain rare. Herein, we present the first description of sauropod teeth from this formation, based on specimens from three separate sites. An isolated tooth and a dentary fragment from the Diamantinasaurus matildae type locality are considered to be referable to that titanosaurian taxon. A single tooth from the D. matildae referred specimen site is similarly regarded as being part of that individual. Seventeen teeth from a new site that are morphologically uniform, and similar to the teeth from the two Diamantinasaurus sites, are assigned to Diamantinasauria. All sauropod teeth recovered from the Winton Formation to date are compressed-cone-chisel-shaped, have low slenderness index values (2.00–2.88), are lingually curved at their apices, mesiodistally convex on their lingual surfaces, and lack prominent carinae and denticles. They are markedly different from the chisel-like teeth of derived titanosaurs, more closely resembling the teeth of early branching members of the titanosauriform radiation. This provides further support for a ‘basal’ titanosaurian position for Diamantinasauria. Scanning electron microscope microwear analysis of the wear facets of several teeth reveals more scratches than pits, implying that diamantinasaurians were mid-height (1–10 m) feeders. With a view to assessing the spatio-temporal distribution of sauropod tooth morphotypes before and after deposition of the Winton Formation, we provide a comprehensive continent-by-continent review of the early titanosauriform global record (Early to early Late Cretaceous). This indicates that throughout the Early–early Late Cretaceous, sauropod faunas transitioned from being quite diverse at higher phylogenetic levels and encompassing a range of tooth morphologies at the start of the Berriasian, to faunas comprising solely titanosaurs with limited dental variability by the end-Turonian. Furthermore, this review highlights the different ways in which this transition unfolded on each continent, including the earliest records of titanosaurs with narrow-crowned teeth on each continent.

Three New Early Middle Eocene Bats (Mammalia: Chiroptera) from Elderberry Canyon, Nevada, USA

We report three new taxa of bats from the late early Eocene to earliest middle Eocene (Bridgerian biochrons Br1b–Br2; ca. 50–48 Ma) Elderberry Canyon Quarry, Sheep Pass Formation, in the Egan Mountain Range of eastern Nevada, USA. Volactrix simmonsae gen. et sp. nov., represented by two dentaries, is tentatively referred to the family ?Onychonycteridae and exhibits a p3 that is much smaller than the p2, a semimolariform p4, and lower molars with a postcristid configuration intermediate between necromantodonty and nyctalodonty. The genus Palaeochiropteryx, a palaeochiropterygid otherwise known from the early and middle Eocene of Europe, is the first representative of its genus and of the family Palaeochiropterygidae outside Eurasia and the Indo-Pakistan subcontinent. Palaeochiropteryx is represented at the site by a partial skeleton with a crushed skull and two left dentaries (one unexposed within the same limestone block but revealed by micro-computed tomography scanning) and is formally named Palaeochiropteryx sambuceus sp. nov. A third taxon, Sonor handae gen. et sp. nov., is a probable vespertilionid, evidenced by a dentary fragment with double-rooted p3 and myotodont lower molar morphology, and provides the earliest occurrence of the family Vespertilionidae in the Western Hemisphere. Despite the small number of specimens, these three new taxa comprise the most diverse Eocene assemblage of bats yet found in a single quarry in the Western Hemisphere.

A new specimen provides insights into the anatomy of Irajatherium hernandezi, a poorly known probainognathian cynodont from the Late Triassic of southern Brazil.

Irajatherium hernandezi is a poorly known non-mammaliaform cynodont from the Late Triassic of southern Brazil. A new specimen of this cynodont was found in recent fieldwork to the type-locality, Sesmaria do Pinhal (Candelária), providing new insights into the anatomy of this mammalian forerunner. This specimen comprises a partial skull preserving the left canine, two left and three right postcanines, and an isolated exoccipital; the left dentary with the canine and postcanines; a fragment of the right dentary; the proximal portion of the left partial humerus; the right scapula; and indeterminate fragments. Based on new material, it is here suggested that I. hernandezi presents: a rostrum broad and short, possibly long as the temporal region; three foramina on the lateral surface of the maxilla, that could correspond to the external openings of the rostral alveolar, infraorbital, and zygomaticofacial canals; a slender zygomatic arch and an absent postorbital bar; a posteriorly wide temporal fossa; a long secondary palate, slightly surpassing the level of the last postcanine tooth; the cerebral hemispheres of the cranial endocast divided by a median sulcus; the scapular blade long and straight, and the postscapular fossa absent in lateral aspect. Finally, I. hernandezi and other tritheledontids were included in a phylogenetic analysis of Eucynodontia. The analysis recovered unresolved relationships for ictidosaurs/tritheledontids, nested within a polytomy with Tritylodontidae and a clade composed by Pseudotherium argentinus, Botucaraitherium belarminoi, Brasilodon quadrangularis, and Mammaliaformes.

A new ctenochasmatid (Pterosauria, Pterodactyloidea) from the late Jurassic of Uruguay

A new ctenochasmatid pterosaur from the Tacuarembó Formation (Late Jurassic of Uruguay), Tacuadactylus luciae gen. et sp. nov. is described, based on a rostrum fragment with spatulated tip and dentary fragments. It closely resembles Gnathosaurus in the orientation of the teeth and the presence of interalveolar concavities. However, a unique combination of synapomorphies distinguishes it from other members of the Ctenochasmatidae. These include the presence of a spoon-shaped spatula not sharply demarcated from the post-spatula rostrum, teeth set in alveoli with raised alveolar borders and deep interalveolar concavities, teeth both anteriorly (i.e. procumbent) and laterally oriented, tooth density of 1.58–2 teeth/cm, tooth separation subequal to tooth size, absence of dorsal concavity, presence of a conspicuous system of vessels and foramina at least in the ventral part of the snout, teeth with veined sub millimetric texture of the enamel and unconspicuous carinae. In a phylogenetic analysis, the new taxon was retrieved as a gnathosaurine closely related to Gnathosaurus. The Tithonian-Berriasian biochron of the latter is coherent with the Late Jurassic age of the Batoví Member, as suggested by conchostracans and theropod teeth. This is one of the few South American Jurassic pterosaur taxa named so far and the oldest ctenochasmatid in this continent. As in Plataleorhynchus and Lonchodraco, Tacuadactylus luciae gen. et sp. nov. shows features that can be correlated with tactile foraging.

A new diapsid with a unique tooth structure from the Middle Triassic (Ladinian) of Germany

ABSTRACT The Middle Triassic was an important time in the evolutionary history of reptiles because it was during this time that many modern groups originated and initially diversified. In this context, the rich fossiliferous deposits of the Ladinian-age Erfurt Formation in southern Germany play an important role in elucidating reptilian diversity during this interval. Here we present an interesting record of a reptile with an unusual dentition. The material comprises a fragment of a left dentary. The teeth are tightly spaced and have chisel-shaped crowns, with the posterolingually extending apices abutting those of the successive teeth and forming a continuous cutting edge. Micro-computed tomography scanning of the jaw fragment revealed the teeth have expanded roots and sit on an open, shallow groove. The Meckelian canal is partially open lingually and a second canal for the inferior alveolar nerve and artery extends parallel to it. Although the preserved anatomical features of the material are insufficient for precise phylogenetic placement, the structure of the robust dentary and its teeth resembles those of some lepidosaurs and certain early Mesozoic marine diapsids. The distinctive morphology of the teeth, combined with the apparent lack of tooth wear, makes it difficult to assess their functional significance. It is interesting that extinct tetrapods with similar tooth morphologies come from strata representing freshwater and brackish-water paleoenvironments, which may serve as an additional line of evidence for future Morpho-functional assessments.

Sheath-tailed bats (Chiroptera: Emballonuridae) from the early Pleistocene Rackham's Roost Site, Riversleigh World Heritage Area, and the distribution of northern Australian emballonurid species.

Sheath-tailed bats (Family Emballonuridae) from the early Pleistocene Rackham’s Roost Site cave deposit in the Riversleigh World Heritage Area, north-western Queensland are the oldest recorded occurrence for the family in Australia. The fossil remains consist of maxillary and dentary fragments, as well as isolated teeth, but until now their precise identity has not been assessed. Our study indicates that at least three taxa are represented, and these are distinguished from other Australian emballonurids based on morphometric analysis of craniodental features. Most of the Rackham’s Roost Site emballonurid remains are referrable to the modern species Taphozous georgianus Thomas, 1915, but the extant species T. troughtoni Tate, 1952 also appears to be present, as well as a very large, as-yet undetermined species of Saccolaimus Temminck, 1838. We identify craniodental features that clearly distinguish T. georgianus from the externally very similar T. troughtoni. Results suggest that the distributions of T. georgianus and T. troughtoni may have overlapped in north-western Queensland since at least the early Pleistocene.

First multituberculate mammals from the Lower Cretaceous of Germany

Multituberculata from the Lower Cretaceous (Barremian–Aptian) Balve locality in Germany are represented by two taxa, the pinheirodontid Bructerodon alatus gen. et sp. nov. and the eobaatarid Cheruscodon balvensis gen. et sp. nov. Bructerodon alatus gen. et sp. nov. is known from an upper premolar (P5) and an upper molar (M1) with a distinct distolingual wing showing three cusps. Cheruscodon balvensis gen. et sp. nov. is represented by a dentary fragment with p4 and isolated teeth (P1, p4, m2). The new taxon is similar to other eobaatarids by its small single-rooted p2, double-routed p3, p4 with a single distolabial cusp, and mesio–distally asymmetric lower molars. It differs from most other eobaatarids by a larger number of serrations (11) and a larger distolabial cusp on p4. Cheruscodon gen. nov. is similar to Arginbaatar from the Lower Cretaceous of Mongolia in having the roots of p4 exposed above the alveolar border and a mesially curved distal root of p4.

Great Evening Bat Ia io (Vespertilionidae, Chiroptera) from the Pleistocene of Vietnam (Lang Trang Cave).

A dentary fragment of a great evening bat Ia io Thomas, 1902 found in 2020 in the Pleistocene deposits of the Lang Trang karstic cave in northern Vietnam is described. This rare species of large tropical bats now inhabits Nepal, eastern India, southern China, Thailand, Laos, and Vietnam and as a fossil is known from the Pleistocene of China. In Vietnam the fossil remains of this species have been discovered for the first time. By the total size and lower molar structure, the specimen from the Lang Trang cave is most similar to the subspecies Ia io peninsulata Soisook et al., 2017 that now occurs in southern Thailand.

Earliest fossils of giant-sized bony-toothed birds (Aves: Pelagornithidae) from the Eocene of Seymour Island, Antarctica

While pelagornithid or ‘bony-toothed’ bird fossils representing multiple species are known from Antarctica, a new dentary fragment of a pelagornithid bird from the middle Eocene Submeseta Formation on Seymour Island, Antarctica represents a species with a body size on par with the largest known species in the clade. Measurements from the partial ‘toothed’ dentary point to a giant body size for the species, although the spacing among the pseudoteeth differs from that published for other pelagornithids. The discrepancy might suggest that previous techniques are not adequate for examination of incomplete material or that another factor such as phylogeny might impact size estimates and comparisons. Combined with a revised stratigraphic position in the early Eocene La Meseta Formation on Seymour Island for the largest pelagornithid tarsometatarsus known, these Antarctic fossils demonstrate the early evolution of giant body size in the clade (by ~ 50 Ma), and they likely represent not only the largest flying birds of the Eocene but also some of the largest volant birds that ever lived (with an estimated 5–6 m wingspan). Furthermore, the distribution of giant-sized pelagornithid fossils across more than 10 million years of Antarctic geological deposits points to a prolonged survival of giant-sized pelagornithids within the southern seas, and their success as a pelagic predatory component of marine and coastal ecosystems alongside early penguins.

Placodont remains (Sauropsida, Sauropterygia) from the Triassic of Hungary (Transdanubian Range and Vill\xe1ny Mountains)

New placodont remains from the Triassic of Hungary are described here. They come from two different tectonic units: the Transdanubian Range Unit representing Alpine type sedimentary basins and the Villány-Bihar Unit that was part of the southern passive margin of the European Plate during the Triassic. The fossils came from four stratigraphic levels with the oldest specimen, a maxilla fragment found in the upper Anisian of Forrás Hill, near Felsőörs (Transdanubian Range). Based on dental morphology, the specimen is referred to here as Paraplacodus broilii. This site is similar in age to the Monte San Giorgio (Switzerland and Italy) locality. A Carnian occurrence of placodonts from this tectonical unit is a dentary fragment and two isolated teeth referred to here as Placochelys placodonta. The youngest specimen from this unit is a placochelyid tooth fragment from the Rhaetian of the Keszthely Mountains (Transdanubian Range). The richest assemblage of new placodont remains is from the Ladinian of the Villány Mountains, southern Hungary. Cranial elements are referred to here as Cyamodus sp. Teeth from this site are similar to that of Cyamodus sp. described from Slovenia, and both assemblages are among the last occurrences of the genus in the European Triassic. The Villány site is considered as a gap locality because of the rarity of Ladinian placodont occurrences in the German-Alpine sedimentary basins.

An omomyid primate from the Pontide microcontinent of north-central Anatolia: Implications for sweepstakes dispersal of terrestrial mammals during the Eocene

A new genus and species of omomyid primate is described from the middle Eocene (Lutetian) Lülük Member of the Uzunçarşidere Formation, Orhaniye Basin, north-central Anatolia, Turkey. This is the first Eocene primate to be reported from the vast area between Switzerland and Pakistan. The new taxon is currently represented by a single dentary fragment, limiting the scope of morphological comparisons that can be made with related taxa. Nevertheless, its dentition differs fundamentally from that of contemporary European microchoerids. The new taxon most closely resembles North American middle Eocene omomyines such as Mytonius hopsoni, and it is therefore interpreted as a member of the Asian/North American omomyine radiation. Its occurrence on the Pontide microcontinent must have resulted from sweepstakes dispersal across the intervening Tethyan barrier that separated the Pontides from adjacent parts of Eurasia during the Lutetian. Sweepstakes dispersal by various terrestrial mammal clades, especially rodents and primates, was facilitated by Eocene greenhouse climatic conditions, which promoted extreme precipitation events and frequent flooding of major river drainages.

To be or not to be: The Hidden Side of Cargninia Enigmatica and Other Puzzling Remains of Lepidosauromorpha from the Upper Triassic of Brazil

ABSTRACT In this contribution, we re-describe the holotype (i.e., the posterior fragment of a left dentary with dentition) of Cargninia enigmatica from the Riograndia Assemblage Zone, Candelária Sequence, Santa Maria Supersequence (Upper Triassic, Brazil), originally considered a member of the Lepidosauria. In addition, two other specimens of lepidosauromorphs from the same locality are described and compared. Broad comparisons suggest that C. enigmatica possesses a unique combination of features, but several key features are widely distributed among basal non-rhynchocephalian lepidosauromorphs and kuehneosaurids. Thus, two possible scenarios are proposed: (1) Cargninia is a basal non-lepidosaurian lepidosauromorph, or (2) it is a basal lepidosaurian. The new specimens are a portion of a right maxilla with teeth (in two fragments) and a fragment of a dentary with teeth. The first specimen is identified as a lepidosauromorph because the maxilla cannot be directly compared with the holotype of C. enigmatica and it is difficult to evaluate if the differences in the dentition (upper versus lower teeth) are the result of intra- or interspecific variation. The dentary, on the other hand, is tentatively referred to C. enigmatica. These specimens together add new clues to understanding the early evolution of Lepidosauromorpha.