The cranial anatomy and taxonomy of Peloneustes philarchus (Sauropterygia,Pliosauridae) from the Peterborough Member (Callovian,Middle Jurassic) of the United Kingdom

Abstract: Peloneustes philarchus is the most abundant pliosaurid from the Peterborough Member of the Oxford Clay Formation (Callovian) of the UK. It is a valid taxon possessing a unique character combination, including a single autapomorphy: the interdentary symphysis is raised dorsally on a narrow platform. Twenty‐one specimens can be positively referred to P. philarchus. However, other specimens previously referred to Peloneustes, from the Peterborough Member near Peterborough, and the lower Oxfordian strata of Marquise, northern France, represent distinct, unnamed taxa. The skull of P. philarchus is described in detail, including new information from an uncrushed, three‐dimensionally preserved specimen and a specimen with a well‐preserved palate. Well‐preserved material clearly indicates that P. philarchus lacked nasals, but possessed a lacrimal. A previously unrecognised ‘palpebral’ forms part of the dorsal orbit margin adjacent to the prefrontal. The number of maxillary (30–31) and dentary (36–44) alveoli, the number of dentary alveoli adjacent to the mandibular symphysis (13–15), the number of foramina on the frontal and jugal, the breadth of the parasphenoid, breadth of the anterior (narial) process of the palatine and the presence of a lappet of the angular that extends onto the posterodorsal surface of the retroarticular process vary among individuals but are not considered sufficient to justify the recognition of new taxa. The presence of an open palpebral–prefrontal suture, the size of the ventral midline tubercle of the basioccipital and the presence of an anterior interpterygoid vacuity seem to vary with body size.     

The nasopalatine ducts and associated structures in the rhesus monkey (Macaca mulatta): topography, prenatal development, function, and phylogeny

Morphological and developmental characteristics of the rhesus monkey nasopalatine duct system and associated primary palatal structures are described along with functional and phylogenetic considerations. Examination of five adult palates and coronal sections of 13 fetal palates together with dissections of a sixth adult specimen and of a 119-day-old fetal palate reveal that the lateral lobes of the tripartate incisive papilla cover clefts leading into the ducts. The ducts pierce the bony palate to enter the nasal fossae in proximity to the incisive suture. The ontogenetic stability of the duct path reflects the retention of ancient duct and primitive choanae relationships and functionally maintains an optimal oral odorant-to-receptor channel. Sixteen timed pregnancy specimens (35-100 days) provided histological material for documenting rostral nasopalatal development. Duct primordia, identified at 35 days, had by 40 days formed the medial duct walls (conjoined septum-papilla from the primary medial palatal component), the lateral duct walls (maxillary processes), and the rostral walls (fused maxillary-intermaxillary components). The caudal walls derive from the fusion of palatal shelves with the papilla (45 days), thus distinguishing primary and secondary fusion modes. Duct epithelial maturation occurs between 70 and 100 days. The absence of a vomeronasal system is attributed to reduction of olfaction in reproductive behavior, while the presence of the coevolved nasopalatine ducts is linked to the persistence of epiglottal-velar valving. The ducts serve as oral food-odor conduits in otherwise functionally separated respiratory and digestive tracts.     

The impact of metamorphosis on the cranial osteology of giant salamanders of the genus Dicamptodon

Pacific giant salamanders (Dicamptodon) rank among the largest terrestrial caudates. Their ontogeny produces two distinct morphs—larval‐neotenic and metamorphosed—which differ in many morphological traits. We identified changes that are initiated by metamorphosis (distinguishing transformed from neotenic specimens) and also recognized age‐related changes occurring irrespective of transformation. During metamorphosis, specimens remodel the palate, rearrange the vomerine dentition, expand the maxilla, broaden the cheek, foreshorten the posterior skull table and develop specific serrated suture patterns in the dermal bones. Instead, large larvae grow a robust pterygoid sutured with a fully ossified trapezoidal vomer and a short maxilla. Small larvae are readily distinguished by tooth count, morphology and arrangement from more advanced larvae. Age‐related features, irrespective of metamorphosis, include pedicellate teeth, morphological differentiation of parasphenoid, enlargement of the orbitosphenoid, distal expansion of columella, and loss of coronoid teeth.     

A rhinesuchid-like temnospondyl from the Permo-Triassic of Uruguay

A new temnospondyl species, Arachana nigra, from the Permo-Triassic Buena Vista Formation of Uruguay is described. The holotypic and only known specimen consists of an almost complete skull lacking most of the snout, the tabular horns and the posterolateral corners of the skull table. As with other specimens from the same unit, Arachana shows a transitional morphology. It shares several characters with rhinesuchids, such as the large size and the general shape of the skull, orbits positioned slightly posterior to the skull roof mid-length, a coarsely pitted dermal ornamentation lacking pustules, and a smoothly convex cheek contour. The palatal ramus of the pterygoid suturing with the vomer, and excluding the palatine and ectopterygoid from the margin of the interpterygoid vacuity, and the presence of a small basioccipital, visible in both occipital and ventral view, also resemble the conditions found in rhinesuchids and other basal temnospondyls. Other characters present in Arachana, however, are commonly found in lydekkerinids, but are absent in almost all rhinesuchids: supratemporal excluded from otic notch; supraorbital and infraorbital sensory sulci encroaching the lacrimal, although lacking a step-like lacrimal flexure; otic notch not deeply incised; post-temporal fenestra large and rounded; occipital condyles well-separated from each other; palatine tooth row behind the palatine tusk reduced; pterygoid corpus slightly ornamented; and presence of an interorbital depression. This combination of primitive and derived characters is consistently present in most components of the Buena Vista fauna, which could thus be transitional between typical Permian and Triassic tetrapod communities found elsewhere. The location of the PTB in the Uruguayan sequence is controversial, mainly due to the lack of clear faunal correlations with other well-known sequences, such as those of southern Africa and Russia. Moreover, the mosaic-like character combinations in most of the recorded tetrapods ally them to both Triassic and Paleozoic groups, and this has complicated even more the possibility of age assignment. Transitional faunas associated with the PTB, such as the Russian Uppermost Permian faunas, could be equivalent to the unique Colonia Orozco fauna. If true, this scenario will substantially change estimates about survivorship rates, suggesting a speciation rate increase in temnospondyls after the Permian-Triassic event. Based on taxonomic, phylogenetic, and geochronologic data, the Buena Vista fauna allows us to quantify faunal turnover across the PTB and in the aftermath of the end Permian extinction event.     

The internal cranial anatomy of the Plesiosauria (Reptilia, Sauropterygia): evidence for a functional secondary palate

In the late 19th Century, the choanae (or internal nares) of the Plesiosauria were identified as a pair of palatal openings located rostral to the external nares, implying a rostrally directed respiratory duct and air path inside the rostrum. Despite obvious functional shortcomings, this idea was firmly established in the scientific literature by the first decade of the 20th Century. The functional consequences of this morphology were only re-examined by the end of the 20th Century, leading to the conclusion that the choanae were not involved in respiration but instead in underwater olfaction, the animals supposedly breathing with the mouth agape. Re-evaluation of the palatal and internal cranial anatomy of the Plesiosauria reveals that the traditional identification of the choanae as a pair of fenestrae situated rostral to the external nares appears erroneous. These openings more likely represent the bony apertures of ducts that lead to internal salt glands situated inside the maxillary rostrum. The 'real' functional choanae (or caudal interpterygoid vacuities), are situated at the caudal end of the bony palate between the sub-temporal fossae, as was suggested in the mid-19th Century. The existence of a functional secondary palate in the Plesiosauria is therefore strongly supported, and the anatomical, physiological, and evolutionary implications of such a structure are discussed.     

Development of the Osteocranium in Natrix natrix (Serpentes,Colubridae) Embryogenesis II: Development of the jaws,palatal complex and associated bones

Snakes differ from the other vertebrates with their hyperkinetic skull. To establish the developmental features of the skull bones, involved in prey capture and ingestion, the Grass snake Natrix natrix (Serpentes, Colubridae) embryos are studied at all the successive stages of embryogenesis. Thirty-five N. natrix embryos are examined. Twenty embryos are studied with histological methods; fifteen embryos are cleared and double-stained with alizarin red and alcian blue. The sequence of appearance and formation of the upper and lower jaw bones, palatal complex and associated bones is described in accordance with the table of developmental stages. New features in the ossification mode of some bones are revealed: each bone, namely, the vomer, septomaxilla and maxilla, is formed from three separate ossification centres. Three ossification centres in the maxilla, two ossification centres in the bodies of the septomaxilla and vomer, as well as the unknown additional ossification centre in the vomer had not been previously described in snake embryos. The new data can be used in further comparative research on the reptile skull development and vertebrate phylogeny.     

Palatal thickening and facial form in Paranthropus: Examination of alternative developmental models

Paranthropus is distinctive among hominoids in its possession of a greatly thickened hard palate. Although traditionally considered a structural adaptation to counter high-magnitude masticatory stress, alternative developmental models are equally viable. Three models of palatal thickening were evaluated in this study. A mechanical model interprets palatal thickening as a compensatory response to increased instability of the midpalatal suture effected by an anterior placement of the masseteric muscle mass. This model predicts that palatal thickness is correlated with the length of the palate posterior to the masseteric tubercle. Two non-mechanical models consider the thickness of the hard palate to be structurally related to and therefore correlated with either 1) the degree to which the premaxilla overlaps the hard palate in the subnasal region or 2) the height of the posterior facial skeleton. The correlation of craniofacial variables was assessed intraspecifically in ontogenetic series of great ape and human crania. Tests of correlation were performed for each comparison using both residuals calculated from reduced major axis regression of the variable of interest against a measure of cranial size and shape ratios. A significant correlation of palatal thickness with posterior facial height in Pan suggests that the unusually thick hard palate of Paranthropus is directly related to the increased posterior facial height characteristic of this taxon. Further evaluation suggests that extreme palatal thickening in these specimens occurred by virtue of their possession of a nasal septum morphology in which the vomer extends onto the superior nasal surface of the premaxilla. Such a morphology would have constrained the palatal nasal lamina to maintain the approximate level of the premaxillary nasal lamina throughout the growth process thereby promoting palatal thickening. Am J Phys Anthropol 103:375–392, 1997. © 1997 Wiley-Liss, Inc.     

内蒙古大青山地区二齿兽类化石的发现

本文记述内蒙古大青山地区脑包沟组中首次发现的脊椎动物化石——边缘大青山兽(Da-qingshanodon limbus)。它具有翼骨腭上枝、基蝶骨小侧架、卷曲的鳞骨等独特构造。依其颅基中轴长、翼间窝长、翼间孔窄,眶前部分短,泪骨与隔颌骨分离等特征,以及在较高层位中发现的大鼻龙类、兽头类等化石,确认大青山兽属典型的晚二叠世二齿兽类型。文中还讨论了二齿兽类鼻区、蝶筛区、翼骨区等构造的演变,“萨拉齐系”与“石千峰群”的岩性和生物的可比性。     

A new specimen of Biseridens qilianicus indicates its phylogenetic position as the most basal anomodont

A new well-preserved basal therapsid skull from the Xidagou Formation, Middle Permian of China, is identified as Biseridens qilianicus. The following synapomorphies distinguish Biseridens as an anomodont and not an eotitanosuchian as previously described: short snout; dorsally elevated zygomatic arch and septomaxilla lacking elongated posterodorsal process between nasal and maxilla. The presence of a differentiated tooth row; denticles on vomer, palatine and pterygoid; contact between tabular and opisthotic; lateral process of transverse flange of pterygoid free of posterior ramus and absence of mandibular foramen exclude it from other anomodonts. Our cladistic analysis indicates Biseridens to be the most basal anomodont, highlights separate Laurasian and Gondwanan basal anomodont clades and suggests that dicynodonts had their origins in the Gondwanan clade. The co-occurrence of the most basal anomodont (Biseridens) together with the most basal therapsid (Raranimus), basal anteosaurid dinocephalians, bolosaurids and dissorophids suggests that the earliest therapsid faunas are from China.     

Morphology of the palate and braincase of Dimetrodon milleri

The palate and partial braincase of the holotype of Dimetrodon milleri (MCZ 1365) are preserved in three dimensions, but have yet to be described in detail. Here, we describe these structures for the first time for this species, and compare them with the better-known specimens of D. limbatus. Interesting characteristics of the morphology include the patterns of articulation of the palatal elements, including the palatine and vomer, and anatomy of the pterygoid in the posterior region of the palatal vacuities. Dimetrodon milleri is found to differ from D. limbatus in the lack of teeth on the ectopterygoid, the shape of the basal process of the epipterygoid, and the anterior extent of the palatine and pterygoid. The two species are similar in the relative position of the basicranial articulation, but differ significantly from that in other sphenacodontids, including Secodontosaurus and Sphenacodon. The evolution of these cranial features will be the subject of future phylogenetic analyses of sphenacodontids.     

四川自贡大山铺蜀龙动物群——简报Ⅴ 两栖类

本文对扁头中国短头鲵(新属新种) (Sinobrachyops placenticephalus gen. et sp. nov.) 的形态特征和分类位置进行简述.标本得自著名的恐龙化石产地——自贡大山铺,产出时代为中侏罗世.中国短头鲵是目前迷齿类中在地史上最年轻的一个属.它的发现使迷齿类在地球上生存时代的上限推移到中侏罗世.     

Heterochrony in fringeheads (Neoclinus) and amplification of an extraordinary aggressive display in the Sarcastic Fringehead (Teleostei: Blenniiformes)

The Sarcastic Fringehead (Neoclinus blanchardi, Teleostei) exhibits an extreme version of a common aggressive display, the “gaping display,” in which an open mouth is presented toward an opponent. Males of this species have extremely long jaws that extend posteriorly well past the posterior margin of the head and are flared laterally during the gaping display. In this study, we explored morphological traits related to this extraordinary display in this and related species of blennies. Morphological modifications include enlargement of the buccopalatal membrane, elongation of the maxilla via an uncalcified posterior extension, and evolution of a novel hinge between the anterior maxilla and lacrimal bones permitting lateral movement of the upper jaw. Geometric morphometry using the truss network system, thin‐plate spline, and PCA of three closely related species of Neoclinus indicate that the elongate maxilla of N. blanchardi most likely evolved via acceleration (faster growth compared to outgroups) and hypermorphosis (continued growth to a larger body size), both forms of peramorphic heterochrony. Coloration and fluorescence of the buccopalatal membrane may also serve to amplify the extraordinary gaping display of the Sarcastic Fringehead.     

The first record of a long-snouted choristodere (Reptilia,Diapsida) from the Early Cretaceous of Ishikawa Prefecture,Japan

A longirostrine choristoderan reptile is described from the Early Cretaceous Tetori Group on the basis of an associated specimen from the Kuwajima Formation, Ishikawa Prefecture. This is the first report of Neochoristodera from Japan. However, the brevirostrine Monjurosuchus has already been reported from the same deposit, and the long-necked Shokawa was recovered from the Okurodani Formation, which is a lateral equivalent of the Kuwajima Formation. This new material demonstrates that the three known choristoderan morphotypes (short-necked longirostrine, short-necked brevirostrine and long-necked brevirostrine) were all present in the Early Cretaceous deposits of the Tetori Group. Until now, the Jiufotang Formation of China was the only deposit where all three were known to have co-occurred.     

A NEW TEMNOSPONDYL FROM THE PERMO-TRIASSIC BUENA VISTA FORMATION OF URUGUAY

Abstract:  A partial skull recovered from conglomerates of the Permo-Triassic Buena Vista Formation in Uruguay belongs to a new species, Uruyiella liminea gen. et sp. nov. This species is characterized by a broadly triangular skull with laterally projecting posterior corners, rhytidosteid-like dermal sculpturing, and orbits positioned close to the skull margin. Uruyiella liminea is distinguished from other temnospondyls by a combination of primitive and derived character states, such as the anterior extent of the palatine ramus of the pterygoid, which excludes the ectopterygoid and most of the palatine from the lateral border of the interpterygoid vacuity, and the absence of both tabular horns and otic notches. A phylogenetic analysis places Uruyiella and the enigmatic Early Triassic Laidleria in a clade to which we attach the family name Laidleriidae. The Plagiosauridae and the Laidleriidae form a clade at the base of Dvinosauria, which is the sister group of a clade that includes Stereospondyli and Archegosauroidea. This result is unexpected because Laidleria and Plagiosauridae are nested deeply within Stereospondyli in most phylogenies. The sister-group relationship of Uruyiella and Laidleria suggests that a ghost lineage for the latter genus extends down into the earliest Triassic and perhaps even into the Late Permian, which in turn would suggest survivorship of the Laidleriidae through the Permo-Triassic extinction event.     

On the vomer in Acrochordidae (Reptilia: Serpentes), and its cladistic significance

It is reported that in certain features the form of the vomer is significantly different in Caenophidia than in Henophidia (except acrochordids). In Henophidia the vomer typically has one or a few apertures for the exit of the vomeronasal nerve from the bony surround of the vomeronasal organ, well- or moderately-developed vertical and horizontal (palatal) posterior laminae, and only a partially-developed cup-like enclosure for the vomeronasal organ. In Caenophidia the vomer typically has very many tiny foramina for the passage of the vomeronasal nerve, the horizontal posterior lamina in particular is much reduced or absent, and the vomer forms a globular enclosure for the vomeronasal organ. A comparison with the vomer in lizards suggests that the henophidian type of vomer is primitive within snakes and the caenophidian type is derived. Scolecophidia are not discussed. The vomer in acrochordids closely resembles that of Caenophidia, and this form of vomerine morphology is proposed as a synapomorphy indicating the strict monophyly of the group acrochordids-Caenophidia. The acrochordids have been treated very differently by various snake taxonomists and their phyletic position has always been highly problematical. The synapomorphy proposed herein contributes to a solution of this problem.     

A new Mastodonsauroid Temnospondyl from the Triassic of Algeria: Implications for the biostratigraphy and palaeoenvironments of the Zarzaïtine Series,northern Sahara

We describe a new species of mastodonsauroid temnospondyl from Algeria, Stanocephalosaurus amenasensis nov. sp., on the basis of two exquisite skulls from a Lagerstätte found in the lowermost formation of the Zarzaïtine Series, Illizi Basin, in the area of “La Reculée”, In Amenas region, Algeria. The new species is characterized by subtriangular nostrils with concave lateral borders; small orbits; postfrontals posteriorly very wide; very elongate parietals; smoothly concave posterior margin of the skull; ovoid anterior palatal vacuities; very posteriorly pointed choanae; oval interpterygoid fenestrae; and a short anterior extension of the cultriform process of the parasphenoid. S. amenasensis is different than the Algerian taxa previously erected by Lehman (1971)–“Parotosaurus lapparenti” and “Wellesaurus bussoni”–which we consider nomina dubia. It enlarges the distribution of the genus in northern Gondwana and supports the Early-Middle Triassic age of the lowermost formation of the Zarzaïtine Series. It also suggests that the local palaeoclimate was very seasonal and these aquatic amphibians died massively in a dewatering sebkha.     

A NEW GENUS AND SPECIES OF SPHENODONTIAN FROM THE GHOST RANCH COELOPHYSIS QUARRY (UPPER TRIASSIC: APACHEAN), ROCK POINT FORMATION, NEW MEXICO, USA

Abstract: We document here a new taxon of sphenodontian, Whitakersaurus bermani gen. et sp. nov., that is also the most complete sphenodontian fossil from the Upper Triassic Chinle Group in the south‐western USA and the first Chinle sphenodontian represented by more than a single fragmentary dentulous element. The holotype was recovered during preparation of block C‐8‐82 from the famous Coelophysis (Whitaker) quarry at Ghost Ranch, New Mexico, and is the most complete small vertebrate recovered from the quarry. Detailed lithostratigraphy and geologic mapping demonstrate that the Whitaker quarry is in the Rock Point Formation of the Chinle Group, so Whitakersaurus is the first sphenodontian reported from this unit. Records of the phytosaur Redondasaurus at the quarry and elsewhere in the Chinle Group demonstrate that the quarry, and thus Whitakersaurus, is of Apachean (late Norian–Rhaetian) age. The sphenodontian specimen consists of incomplete left and right dentaries, a partial left? maxilla?, and impressions of a probable palatal element, all of which preserve multiple teeth. Whitakersaurus is distinct from other sphenodontians in possessing a unique combination of the following features: marginal dentition pleurodont anteriorly and posteriorly acrodont; pronounced heterodonty in dentary, with as many as 15 smaller, peg‐like teeth anteriorly and several larger, posterior teeth that are conical and striated; faint radial ornamentation of posterior tooth crowns; presence of c. 19 dentary teeth; and absence of a distinct flange on posterior teeth. Numerous other details distinguish it from both more primitive and more derived taxa. Whitakersaurus, therefore, helps to document further mosaic evolution and an extensive diversification event of sphenodontians during Triassic time. Although sphenodontian taxa are relatively easily recognized, widely distributed, and common small‐ or microvertebrate fossils, the long stratigraphic ranges of taxa known from multiple specimens hinders their utility as index fossils with which to correlate strata across Pangaea.     

A new cryptoclidid Plesiosaur from the Oxfordian (Late Jurassic) of Cuba

Cryptocleidus ? cuervoi caroliDE LA TORRE & ROJAS, 1949, a partial skull with associated mandible and atlas-axis from the Oxfordian of Cuba, has been completely prepared for the first time. It is here redescribed and assigned to a new cryptoclidid genus, Vinialesaurus, for which the species caroli is retained. Vinialesaurus is mainly diagnosed by palatal characters such as double internal nares, an anteriorly rounded vomer and a lack of anterior interpterygoid vacuities. It shares with other cryptoclidids large orbits and external nares, a small vertical jugal and a reduced tooth ornamentation. The occurrence of Vinialesaurus caroli in association with pliosauroids, ophthalmosaurian ichthyosaurs, metriorhynchid crocodilians and pleurodiran marine turtles, strongly suggests that a marine seaway was present in the Caribbean during the Oxfordian, connecting the western Tethys with the Oriental Pacific.