Complete Skull Research Articles

A new stem-tetrapod fish from the Middle–Late Devonian of central Australia

ABSTRACT Remote Devonian exposures in central Australia have produced significant but highly fragmentary remains of fish-grade tetrapodomorphs. We describe a new tetrapodomorph from the Middle–Late Devonian (Givetian–Frasnian) Harajica Sandstone Member of the Amadeus Basin, Northern Territory, which is represented by several nearly complete skulls along with much of the body and postcranial skeleton. The new form has a posteriorly broad postparietal shield, broad, triangular extratemporal bones, and a lanceolate parasphenoid. The spiracular openings are particularly large, a character also recorded in elpistostegalians and Gogonasus, demonstrating that these structures, suggestive of spiracular surface air-breathing, appeared independently in widely differing nodes of the stem-tetrapod radiation. A phylogenetic analysis resolves the new form within a cluster of osteolepidid-grade taxa, either as part of a polytomy or as the most basally branching representative of a clade containing ‘osteolepidids,’ canowindrids, and megalichthyids.

Pliocene fossils support a New Zealand origin for the smallest extant penguins

AbstractA late Pliocene (3.36–3.06 Ma) exposure of the Tangahoe Formation on the North Island of New Zealand preserves close fossil relatives of many extant seabird clades. Here, we report an extinct member of the little penguin (Eudyptula Bonaparte, 1856) lineage from the Tangahoe Formation—the smallest extinct crown penguin yet known. Eudyptula wilsonae n. sp. is based on the nearly complete skulls of an adult and a fledged but immature individual. Both skulls show more slender proportions than modern little penguins and precede genome-derived estimates for the divergence between Eudyptula minor minor Forster, 1781 (endemic to New Zealand) and Eudyptula m. novaehollandiae Stephens, 1826 (native to Australia and recently established in New Zealand). This raises the possibility that the fossil taxon represents a lineage directly ancestral to extant little penguins. Our results support a Zealandian origin for little penguins, with subsequent Pleistocene dispersal to Australia and a more recent Holocene range expansion of Eudyptula m. novaehollandiae back into New Zealand.UUID: https://zoobank.org/a415f70a-e441-4920-85e0-75f6457577ea

A nearly complete skull of the sauropod dinosaur Diamantinasaurus matildae from the Upper Cretaceous Winton Formation of Australia and implications for the early evolution of titanosaurs.

Titanosaurian sauropod dinosaurs were diverse and abundant throughout the Cretaceous, with a global distribution. However, few titanosaurian taxa are represented by multiple skeletons, let alone skulls. Diamantinasaurus matildae, from the lower Upper Cretaceous Winton Formation of Queensland, Australia, was heretofore represented by three specimens, including one that preserves a braincase and several other cranial elements. Herein, we describe a fourth specimen of Diamantinasaurus matildae that preserves a more complete skull-including numerous cranial elements not previously known for this taxon-as well as a partial postcranial skeleton. The skull of Diamantinasaurus matildae shows many similarities to that of the coeval Sarmientosaurus musacchioi from Argentina (e.g. quadratojugal with posterior tongue-like process; braincase with more than one ossified exit for cranial nerve V; compressed-cone-chisel-like teeth), providing further support for the inclusion of both taxa within the clade Diamantinasauria. The replacement teeth within the premaxilla of the new specimen are morphologically congruent with teeth previously attributed to Diamantinasaurus matildae, and Diamantinasauria more broadly, corroborating those referrals. Plesiomorphic characters of the new specimen include a sacrum comprising five vertebrae (also newly demonstrated in the holotype of Diamantinasaurus matildae), rather than the six or more that typify other titanosaurs. However, we demonstrate that there have been a number of independent acquisitions of a six-vertebrae sacrum among Somphospondyli and/or that there have been numerous reversals to a five-vertebrae sacrum, suggesting that sacral count is relatively plastic. Other newly identified plesiomorphic features include: the overall skull shape, which is more similar to brachiosaurids than 'derived' titanosaurs; anterior caudal centra that are amphicoelous, rather than procoelous; and a pedal phalangeal formula estimated as 2-2-3-2-0. These features are consistent with either an early-branching position within Titanosauria, or a position just outside the titanosaurian radiation, for Diamantinasauria, as indicated by alternative character weighting approaches applied in our phylogenetic analyses, and help to shed light on the early assembly of titanosaurian anatomy that has until now been obscured by a poor fossil record.

Correction to: A complete skull of a stem mammal from the Late Triassic of Brazil illuminates the early evolution of prozostrodontian cynodonts

Correction to: A complete skull of a stem mammal from the Late Triassic of Brazil illuminates the early evolution of prozostrodontian cynodonts

A New Specimen of Sinosaurus triassicus (Dinosauria: Theropoda) from the Early Jurassic of Lufeng, Yunnan, China

ABSTRACT The holotype of Sinosaurus triassicus is poorly preserved, and no previous research has focused exclusively on its anatomy. This research reports a new specimen recovered near the locality of the holotype of S. triassicus including a complete skull with mandible and 11 cervical vertebrae. Three newly identified traits are proposed to be unique of the species – (1) a vertical crest developed dorsoventrally from the ventral portion of the maxilla to the nasal crest; (2) ventral border of the antorbital fenestra formed mostly by the anterior process of the jugal; and (3) a fenestra between the nasal, the lacrimal and the prefrontal. This research provides new information on the cranial anatomy of this species as well as the genus Sinosaurus, offering more accessibility for later research concerning the evolution of early deriving neotheropods.

The earliest dipodomyine heteromyid in North America and the phylogenetic relationships of geomorph rodents.

Dipodomyine heteromyids (kangaroo rats and mice) are a diverse group of arid-adapted ricochetal rodents of North America. Here, a new genus and species of a large dipodomyine is reported from early Miocene-aged deposits of the John Day Formation in Oregon that represents the earliest record of the subfamily. The taxon is known from a single specimen consisting of a nearly complete skull, dentary, partial pes, and caudal vertebra. The specimen is characterized by a mosaic of ancestral and highly derived cranial features of heteromyids. Specifically, the dental morphology and some cranial characteristics are similar to early heteromyids, but other aspects of morphology, including the exceptionally inflated auditory bullae, are more similar to known dipodomyines. This specimen was included in a phylogenetic analysis comprising 96 characters and the broadest sampling of living and extinct geomorph rodents of any morphological phylogenetic analysis to date. Results support the monophyly of crown-group Heteromyidae exclusive of Geomyidae and place the new taxon within Dipodomyinae. The new heteromyid is the largest known member of the family. Analyses suggest that large body size evolved several times within Heteromyidae. Overall, the morphology of the new heteromyid supports a mosaic evolution of the open-habitat adaptations that characterize kangaroo rats and mice, with the inflation of the auditory bulla appearing early in the group, and bipedality/ricochetal locomotion appearing later. We hypothesize that cooling and drying conditions in the late Oligocene and early Miocene favored adaptations for life in more open habitats, resulting in increased locomotor specialization in this lineage over time from a terrestrial ancestor.

An Early Miocene kentriodontoid (Cetacea: Odontoceti) from the western North Pacific, and its implications for their phylogeny and paleobiogeography.

So-called 'kentriodontids' are extinct dolphin-like odontocetes known from the Early to Late Miocene worldwide. Although recent studies have proposed that they were monophyletic, their taxonomic relationships still remain controversial. Such a controversy exists partly because of the predominance of primitive morphologies in this taxon, but the fact is that quite a few 'kentriodontids' are known only from fragmentary skulls and/or isolated periotics. A new 'kentriodontid' Platysvercus ugonis gen. et sp. nov. is described based on a nearly complete skull from the upper Lower Miocene Sugota Formation, Akita Prefecture, northern Japan. Based on the phylogenetic analysis of P. ugonis described here, the monophyly of the 'kentriodontids' is confirmed, and it is recognized as the superfamily Kentriodontoidea. This new superfamily is subdivided into two families as new ranks: Kentriodontidae and Lophocetidae. Based on the paleobiogeographic analysis of the Kentriodontoidea, their common ancestor emerged in the North Pacific Ocean and spread over the Northern Hemisphere. Initial diversification of the Kentriodontidae in the North Pacific Ocean and the Lophocetidae in the North Atlantic Ocean was recognized as a vicariance event. The diversification and extinction of the Kentriodontoidea could have been synchronously influenced by climate events during the Middle Miocene.

A New Giant Petrel (Macronectes, Aves: Procellariidae) from the Pliocene of Taranaki, New Zealand

A new species of giant petrel, Macronectes tinae sp. nov., is described from the Pliocene deposits of South Taranaki, New Zealand. The holotype is a near complete skull and the paratype a fragmentary left humerus; both come from the Tangahoe Formation, dating from the late Pliocene (Piacenzian or “Waipipian”; age estimated as ca. 3.36–3.06 Ma). The new species of giant petrel is the first fossil Macronectes ever reported. It is morphologically similar to the two present-day Macronectes spp., but it was a smaller bird. The skull is diagnosed by its overall smaller size, a proportionately longer apertura nasi ossea, and potentially by a shorter os supraocciptale. The humerus is diagnosed from both species by a proportionately less deep shaft, a more prominent medial portion of the epicondylus ventralis, and a larger and fusiform fossa medialis brachialis. The Tangahoe Formation is proving to be a remarkable source of marine vertebrate fossils and an important piece of the puzzle in understanding the evolution and biogeography of seabirds.

A complete skull of a stem mammal from the Late Triassic of Brazil illuminates the early evolution of prozostrodontian cynodonts

A complete skull of a stem mammal from the Late Triassic of Brazil illuminates the early evolution of prozostrodontian cynodonts

Fossils Explained 83: Diversity of skull morphology in the Titanosauria

Titanosaurs were a globally distributed group of sauropod dinosaurs. They had diverse forms and a wide-gauge stance, with a few of their species reaching immense sizes, such as Argentinosaurus huinculensis and Patagotitan mayorum (reaching >35 m in length). There are about 100 valid titanosaur species known so far, but most of the originally described species are no longer valid, due to the incomplete nature of fossil materials. Our understanding of titanosaur skull morphology is based on very few incomplete fragmented cranial materials and findings of the complete skull are even rarer. Understanding the skull morphology of extinct animals helps palaeontologists make deductions of feeding mechanisms and also provide an idea about their appearance when they were alive. Diversity in titanosaur skull morphology is greater than that of any other sauropod clade, indicating diversity in feeding mechanism among these dinosaurs. Titanosaurs were the last surviving clade of sauropod dinosaurs, occupying nearly every ecological niche around the world during the Late Cretaceous, and resulting in a rich diversity in this group. This article highlights diversity in the basic structure of sauropods with special emphasis on titanosaur skull morphology.

A new podocnemidid (Pleurodira: Pelomedusoides) from the Eocene of north-western Argentina, with comments on its evolutionary relationships and palaeoenvironmental settings

We report a new small podocnemidid, Gestemys powelli gen. et sp. nov., based on one nearly complete skull, lower jaw, two shells, and remains of the appendicular skeleton belonging to two specimens from the Eocene Geste Formation of the San Antonio de la Cobres Basin, Salta Province, north-western Argentina. As in other podocnemidid genera, Gestemys exhibits a fully developed and medially extensive cavum pterygoidei, an incisura columellae auris enclosing the stapes and Eustachian tube, and lacks an exoccipital quadrate contact. Gestemys powelli bears a huge foramen palatinum posterius and a short pterygoid flange that does not reach the basisphenoid suture, exposing the cavum pterygoid. Phylogenetic analyses place Gestemys powelli as a member of Podocnemididae more closely related to Erymnochelyinae than Podocnemidinae. In regards to the palaeoenvironmental settings of the Palaeogene formations (Maíz Gordo and Geste) of north-western Argentina, at least two features differentiate the palaeoenvironment where G. powelli was recovered and those of other podocnemidid turtles from the Maíz Gordo Formation: 1) G. powelli was found in situ with very little re-working; and 2) in contrast to the muddy rocks indicating the marginal lacustrine setting and humid climate of the Maíz Gordo Formation, G. powelli is associated with a coarse-grained floodplain setting and a dry, temperate climate. Such differences highlight the contrasting environmental dynamics in which podocnemidid turtles lived during the Palaeogene. http://zoobank.org/urn:lsid:zoobank.org:pub:0E631DA2-053F-4BD6-91BD-2401F34A5777

Novel information on the cranial anatomy of the tapejarine pterosaur Caiuajara dobruskii.

Caiuajara dobruskii is a tapejarid pterosaur from the Cretaceous of the 'Cemitério dos Pterossauros' (pterosaur graveyard) site, a unique pterosaur bonebed which is located at the municipality of Cruzeiro do Oeste (Paraná, Brazil). Preliminary inferences on Caiuajara morphology were founded on a few partial skeletons, with no detail on the skull anatomy. Here we describe a new specimen from the pterosaur graveyard site, which corresponds to the most complete skull of Caiuajara dobruskii known so far. Furthermore, we describe and compare other specimens including the holotype, a paratype, and several other undescribed specimens. The new specimen preserves the posterior portion of the skull, allowing a better comprehension of its morphology and provides an appreciation of the anatomic structures of the basicranium, enabling better interpretation of this region. We also described the lower jaw of Caiuajara, reporting a unique feature of its symphyseal which adds to the diagnosis for the species. A variability in the premaxillary crest is also noted in different specimens of Caiuajara, which might be interpreted as sexual dimorphism or ontogenetic variability. Therefore, those new findings allow a better comprehension of its skull and enables a more precise comparison between the skulls of those extinct flying reptiles.

The endocast of Phuwiangosaurus sirindhornae from the Lower Cretaceous of Thailand

Among skeletons, the cranial elements of sauropod are typically fragmented and rare, despite the increasing number of elements and almost complete skulls discovered or redescribed in the last decades. Phuwiangosaurus sirindhornae was one of the most completely sauropod braincase known from Southeast Asia. Here we describe an endocast of Phuwiangosaurus, including the hindbrain, cranial nerves, blood vessels, and inner ear. The shape of the dural peak was similar to Camarasaurus and the bulbous feature of the pituitary gland was similar to basal titanosaur. The trigeminal nerve exits the braincase through more than one opening. The abducens nerve passes the pituitary fossa laterocaudally, and the hypoglossal nerve exiting the braincase through two canals as in Sarmientosaurus, some titanosaurs, and early-branching macronarians. There is, one exit of CN XII on each side of the occipital condyle as in advanced titanosaurs. The anterior semicircular canal is elevated dorsally and larger than the posterior semicircular canal similar to Giraffatitan, Malawisaurus, Sarmientosaurus and Diamantinasaurus. Our observations are congruent with the interpretation of Phuwiangosaurus is a transitional form between the somphospondylan and titanosaurian despite some works put it in a basal position within somphospondylan sauropods.

A new skull of early cetacean Remingtonocetus harudiensis from the Eocene of Kutch Basin, India

A nearly complete skull of Remingtonocetus harudiensis was discovered from the Harudi Formation of the Kutch Basin, western India. Though several specimens have been collected over the last two decades by earlier workers, this skull shows variations in morphology within the species that were not known earlier. Hence, this finding is significant because it helps in expanding our knowledge of the skull morphology with the addition of characters such as the larger size of the skull, the difference in dental morphology, and the two-ridged external nasal feature and our understanding of how the molar morphology can vary within the same species. The newly excavated skull is the largest Remingtonocetus skull so far discovered and is similar to the size of Dalanistes ahmedi from Kutch, India and from Baluchistan, Pakistan. Thus, the range of the overall body size of the species will change considerably towards the higher side nullifying a major distinction between Dalanistes and Remingtonocetus. The new skull was excavated from the chocolate brown shales of the clastic facies of the Harudi Formation, in the inner ramp of a lagoonal phase. It is approximately 4 m above the nodular limestones from which the other Remingtonocetus materials were previously described. The limestone represents the carbonate facies of the Formation formed in a middle to outer ramp setting. An emended diagnosis of R. harudiensis is provided in this study. The Bartonian Harudi Formation of the Kutch Basin, thus, becomes unique in having Remingtonocetus specimens discovered from two different lithological facies from both the inner and outer ramp settings.

First occurrence of the eutherian mammal Asioryctes nemegtensis from the Upper Cretaceous Djadokhta Formation, Gobi Desert, Mongolia, and a revised alpha taxonomy based on the skull and dentition

ABSTRACT We report on the discovery of new skulls and dentitions documenting a broader geographic and stratigraphic range for the eutherian mammal Asioryctes nemegtensis. Originally discovered in the Upper Cretaceous Barun Goyot Formation of the Gobi Desert, Mongolia, A. nemegtensis has been hypothesized to be absent from the Djadokhta Formation, another Upper Cretaceous Gobi Desert formation. This distinction has previously contributed to an emphasis on faunal and age dissimilarity between the two sets of Cretaceous rocks. Here we report four new specimens of A. nemegtensis from the Djadokhta Formation and document its first co-occurrence with its sister taxon, Ukhaatherium nessovi. The new specimens reveal additional details about the cranial and dental anatomy of asioryctitheres and prompt an alpha taxonomic revision and emended diagnosis for A. nemegtensis. Among the new specimens are a nearly complete skull and several articulated jaws, which provide new information on tooth occlusion. These discoveries are an additional datapoint indicating that some Upper Cretaceous faunal assemblages in Mongolia are not as distinctly different in composition and age as has been previously hypothesized.

Description of the first Cretaceous (Santonian) articulated skeletal lungfish remains from South America, Argentina

The fossil record of dipnoans is mostly represented by tooth plates and jaw bones, whereas nearly complete or complete skulls are rare. Here, we describe a new dipnoan from the Santonian (Upper Cretaceous) of Patagonia (Argentina) using three-dimensional renderings generated by CT scans. It consists of a near-complete skull and postcranial material. Rinconodus salvadori n. gen., n. sp. is diagnosed by a combination of features, such as medial series composed of two unpaired bones, mediolateral series composed of two paired bones, lateral series with at least one bone, medial edge of tooth plates longer than the lingual edge and equally curved, upper tooth plates contiguous or close to one another with five denticulations, lower tooth plates widely separated with four denticulations, first denticulation of upper tooth plates longer and thinner than the remaining denticulations, and posteriorly curved, first denticulation of lower tooth plates relatively straight and longer than the remaining ones, among other characters. The new species is based on the first two nearly complete Santonian dipnoan skulls from South America. Moreover, the materials presented here are the geologically youngest dipnoan remains consisting of a near-complete skull and postcranium from the Cretaceous of Gondwana.

A new species of Pinnarctidion from the Pysht Formation of Washington State (U.S.A.) and a phylogenetic analysis of basal pan-pinnipeds (Eutheria, Carnivora)

ABSTRACT A nearly complete skull and limited postcrania (SDSNH 146624), from the upper Oligocene of the Pysht Formation (Clallam County, Washington State, U.S.A.), represent a new species of Pinnarctidion, a pan-pinniped previously restricted to California and Oregon. Here, we describe SDSNH 146624 in detail and present results of a comprehensive phylogenetic analysis of early-diverging pan-pinnipeds. Pinnarctidion iverseni sp. nov., recognized on the basis of this specimen, is diagnosed by its posteriorly broad palate, anteriorly narrow rostrum, dorsoventrally deep zygomatic arches, and posterior accessory cusps on P3–4. Phylogenetic analysis recovered P. iverseni as most closely related to P. bishopi from the Jewett Sand of California’s Central Valley. The well-preserved and reasonably complete skull and upper dentition of SDSNH 146624 help clarify relationships among the proximal outgroups of crown clade pinnipeds.

Complete skull of Bothriogenys fraasi (Mammalia, Artiodactyla, Anthracotheriidae) from the Early Oligocene, Fayum, Egypt

Bothriogenys is an endemic African anthracothere (Mammalia, Artiodactyla), which was first documented at the beginning of the last century by Schmidt in 1913. It is one of the most common genera and species that were unearthed from Early Oligocene deposits of North Africa, like those of the Fayum Depression, Egypt. It has been thought that the genus Bothriogenys probably give rise to the Early Miocene Brachyodus that dispersed to Europe and Asia around 20 million years ago. Here, we describe a complete skull of B. fraasi. The specimen is a nearly complete cranium with right canine, left and right upper first premolar‐upper third molar. The new skull has two mesial cristae on the upper premolars, three cristules on the metaconule and the upper fourth premolar has three roots. The main palatine foramina are located at the level of the mesial border of the upper fourth premolar and the internal choanae open well behind the upper molar. The cranial bones and the dentition indicate that Bothriogenys is located at the basal part of the subfamily Bothriodontinae and very close to early Miocene Brachyodus. If so Bothriogenys was likely among the first anthracotheriids to enter Africa. Continued anthracothere development and evolution ultimately gave rise to Early Miocene Brachyodus.

Cranioplasty for Skull Defects With Polypropylene Abdominal Wall Mesh

Cranioplasty is a well-established common surgery in the practice of neurosurgery and craniofacial surgery. In young patients, complete skull defect closure by bone splitting may be troublesome due to the difficulty to obtain enough bone area. In such cases, sometimes the authors need to use allografts, which may not be widely available in rural practice. In this study, the authors present the series of cranioplasty with polypropylene mesh, which is widely used in abdominal wall closure. Nine patients with depressed compound skull fracture were treated by performing this technique. Selection criteria were: compound depressed skull fractures in which bones were fragmented in a way not able to be reconstructed with and leaving a skull defect, small-sized or relatively medium-sized skull defects, and skull defects not located on the sharp curvatures of the skull which needs firm bended meshes. All patients were male and their ages ranged between 8 months and 36 years.The skull bone defect was reconstructed with polypropylene abdominal wall mesh, which was sutured circumferentially with the galeal tissue. Skull defects were successfully treated in all patients. The follow-up period ranged from 4 to 13 months. One patient with a history of alcoholism and neglectance developed a wound infection after 3 weeks of surgery. This patient was treated successfully with intravenous antibiotics without the need to remove the mesh. There were no complications in the remaining 8 patients. Polypropylene mesh is a cheap and effective material for the reconstruction of small-sized or medium-sized skull defects. It can be a good alternative in rural practice and/or low economic communities, when other cranioplasty materials are not available.

New remains of Eleutherocercus (Xenarthra, Cingulata, Glyptodontidae) from the Pampean and Northwestern regions of Argentina: morphology and phylogeny of late Neogene Doedicurinae

ABSTRACT The subfamily Doedicurinae is a monophyletic group of glyptodonts with their own anatomical features and is mostly known on the basis of the Pleistocene genus Doedicurus, one of the largest recorded taxa. The most distinctive character of the subfamily, unique within Cingulata, include the absence of ornamentation with large foramina, on the exposed surface of the carapace osteoderms. In terminal forms of the late Pleistocene, osteoderms have large foramina which tend to cross the entire thickness. The knowledge of the late Neogene diversity of the clade, as well as its evolutionary and geographical history, has increased in recent years, with important records in Argentina, where two late Miocene-Pliocene species are recognised: Eleutherocercus solidus from Catamarca and Tucumán provinces, and Eleutherocercus antiquus from Buenos Aires province. The most complete skull of E. antiquus from the early Pliocene Monte Hermoso Formation (ca. 5–4.2 Ma) is reported here. The specimen studied shows a conspicuous pathology on the parietal bones, first reported for fossil cingulates. In addition, the carapace of E. solidus is first described, on the basis of a partially complete specimen from the late Miocene-Pliocene (unknown stratigraphic level) from Tucumán province. Previous phylogenetic hypotheses of the relationships within the Doedicurinae, as well as their relationship with the remaining clades of Glyptodontidae, is tested in this study, adding new synapomorphies to the subfamily. The comparative study suggests that a third species previously proposed (E. paranaensis) from the ‘Mesopotamiense’ (late Miocene, Northeastern region of Argentina), must be considered as Eleutherocercus sp. Since their oldest record in the late Miocene, the latitudinal distribution of the Doedicurinae seems to have expanded rapidly reaching middle latitudes, particularly during the Pliocene, but during the Pleistocene (particularly the final lapse of this period), they began to retract latitudinally.