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Ptychodus (Elasmobranchii, Ptychodontidae) is an enigmatic durophagous shark that lived in Cretaceous seas. Based on multiple articulated tooth plates of Ptychodus mortoni from the Niobrara Chalk in Kansas, the dental pattern of P. mortoni and its paleobiological implications were examined. Each tooth plate consists of one medial tooth row and about nine lateral tooth rows on each side. One individual shark possesses a total of slightly over 550 teeth, with approximately 220 functional upper teeth and 260 functional lower teeth. The largest tooth plate of the species likely measured about 55 cm in length and 45 cm in width. Although this study does not resolve the ordinal placement of Ptychodontidae, it demonstrates that there are two different patterns of tooth plate organization in Ptychodus: a plesiomorphic condition characterized by juxtaposed, non-overlapping tooth rows (e.g., P. decurrens, P. marginalis, and P. occidentalis) and an apomorphic condition characterized by imbricated tooth rows (e.g., P. mortoni). It is hypothesized here that the imbrications of tooth rows in P. mortoni likely helped distribute the bite-induced load on its dentition more widely, and its sharp-tipped crowns were effective in shattering animals with comparably thin, brittle shells (e.g., bivalves and crustaceans). The recognized difference in tooth plate organization adds another level of complexity to the dental evolution of Ptychodus as well as to the already complex evolutionary history of predatory behaviors in cartilaginous fishes. [ABSTRACT FROM AUTHOR]

A partial reptile skull collected from the Lower Triassic (Induan) Barendskraal locality of South Africa is referable to the procolophonid parareptile Sauropareion anoplus. The specimen comprises the left side of the skull roof, palate, and mandible, and preserves areas not preserved or accessible in the skulls of previously published specimens, including fragmentary remains of the premaxilla, the anterior end of the maxilla, and the anterior end and lingual aspect of the mandible. The maxilla exhibits a maxillary depression that is similar in both shape and relative size to that seen in Procolophon trigoniceps, an anterolateral maxillary foramen that is indistinguishable from those seen in other procolophonoids, and 11 conical teeth. The suborbital foramen is formed ventrally by the palatine and the ectopterygoid. The dentary and the coronoid are fused together indistinguishably in lateral aspect. The marginal teeth appear to be anchored to the jaws by bone of attachment. The dentary teeth are exposed in lingual aspect and appear to be ankylosed to the summit of the bone, suggesting acrodont tooth implantation. Tooth replacement is seen in these teeth, where the lingual surface of a single tooth crown base in the middle of the dentary series is excavated for the apex of a replacement tooth crown, but the excavation does not extend ventrally onto the lingual surface of the bone. Considering that no extant reptiles with acrodont tooth implantation exhibit tooth replacement or bone of attachment, we tentatively regard protothecodonty to be present in S. anoplus. [ABSTRACT FROM AUTHOR]

All previous records of the lamniform shark, Archaeolamna kopingensis, are based on isolated teeth. Here we describe a partial skeleton from the Sharon Springs Formation of the Pierre Shale Group of western Kansas, U.S.A. The specimen includes portions of the upper and lower jaws with articulated teeth. The dentition consists of two files of upper and lower anterior teeth that, together with a single file of intrabullar intermediate teeth, are housed in a dental bulla, as well as multiple files of lateral teeth, along with at least two files of lower symphysial teeth and a single file of upper symphysial teeth. The intrabullar intermediate tooth is slightly shorter than the other anterior teeth and has a median cusp with distinctive distal curvature. The dental sequence of A. kopingensis is unique among both extinct and extant lamniforms. Associated with the jaws are fragments of the neurocranium and multiple vertebral centra. A sagittal section through a centrum shows that this shark deposited 18 annual marker bands after its birth and adult size was attained by the 10th band. The robust but penetrating tooth morphology and large jaw circumference suggest that A. kopingensis likely fed upon large prey items. [ABSTRACT FROM AUTHOR]

Metriorhynchids were a peculiar group of fully marine Mesozoic crocodylomorphs. The derived genera Dakosaurus and Geosaurus exhibit a macroevolutionary trend towards extreme hypercarnivory, underpinned by a diverse array of craniodental adaptations, including denticulate serrated (ziphodont) dentition. A comparative analysis of serrations in Metriorhynchidae shows that known Dakosaurus species had conspicuous denticles, in contrast to the microscopic denticles of Geosaurus. A new tooth from the Nusplingen Plattenkalk of Germany provides evidence for a previously unknown large species of Geosaurus. Metriorhynchid specimens from the upper Kimmeridgian-lower Tithonian of Southern Germany show that ziphodont species of Dakosaurus and Geosaurus co-occurred in the Nusplingen and Solnhofen Seas. Although these genera are similarly denticulate, they diverge in overall crown morphology. Therefore, resource/niche partitioning via craniodental differentiation is posited as maintaining two contemporaneous genera of highly predatory metriorhynchids. Additionally, the new generic name Torvoneustes is proposed for “Geosaurus” carpenteri, the only known metriorhynchid with false-ziphodont dentition. A cladistic analysis shows that ziphodont dentition may have evolved independently in Dakosaurus and Geosaurus, or been acquired earlier by their common ancestor and secondarily lost in Torvoneustes and related taxa. [ABSTRACT FROM AUTHOR]

The article describes dentary assignable to the holotypic specimen of Suuwassea emilieae. The dentary is small and the posterior two-thirds of the ventral margin of the dentary is nearly linear. It has been found that the dentary bears nine alveoli and the last alveolus occurs at a position just over one-third of the total dentary length from the symphysis. The dentary arches in dorsal view appears gently toward the symphysis, although the tooth row bows outward near the anterolateral corner of the dentary. It has been found that the external surface of dentary is smooth without anteriorly projected prominence.

Much of Mesozoic diversity within the lungfishes (Osteichthyes: Dipnoi) has traditionally been relegated to the genus Ceratodus, primarily on the basis of the highly stereotypical dental plates characteristic of post-Devonian lungfishes. The new genus Potamoceratodus contains the single species P. guentheri (Marsh, 1878), comb. nov. Newly discovered material allows clarification of the features of this species, including description of a complete skull roof and partial palate. The new genus can be differentiated from the European Ceratodus on the basis of characters of the skull roof, palate, and dentition, including lack of tubercular ornamentation of the skull roof, modest convexity of the dorsal skull roof, absence of sensory sulci anteriorly in the EF bone, and an enlarged and elongate anterior odontode series on the pterygoid dental plate. The North American Ceratodus record is reexamined in light of more complete material from the Temple Canyon localities of the Morrison Formation of Colorado, USA. Ceratodus is found to be an assemblage of forms with disparate cranial morphology. The succession of North American lungfish communities in the late Paleozoic and Mesozoic is most characteristic of serial replacement rather than in situ evolution, and it is possible that the isolation of North America subsequent to the breakup of Laurentia contributed to the regional extinction of lungfishes in North America. [ABSTRACT FROM AUTHOR]

The Cambay Formation at Vastan Mine in Gujarat, western India, has yielded the oldest artiodactyls and other land mammals from India, which are dated as middle Ypresian (∼53 Ma) based on foraminiferids. Here we describe new dentitions, including dentaries and upper teeth of Diacodexis indicus (= Gujaratia indica) from Vastan. These provide better characterization of this Asian diacodexeid (Artiodactyla: Mammalia) than was available earlier. A new combination, Diacodexis indicus, is proposed in place of Gujaratia indica, and G. pakistanensis is referred back to Diacodexis. A new, very small species of Diacodexis, D. parvus, is reported based on isolated teeth. Whereas D. indicus is approximately the size of the largest known species of Diacodexis, D. parvus represents the smallest recorded species of the genus and is one of the smallest known artiodactyls. Diacodexeidae indet. from Vastan is exemplified by a fragment of a dentary and an upper molar, which are of intermediate size. Several isolated teeth represent a new genus and species, unrelated to Diacodexeidae, and are assigned to Artiodactyla indet. pending discovery of more adequate specimens. Early Eocene diacodexeid postcrania are described for the first time from India. Early Eocene artiodactyls from India are phenetically close to Euroamerican species of Diacodexis, providing further evidence of phylogenetic connections particularly with European faunas. A few postcranial features of the Vastan artiodactyls are also seen in primitive archaeocetes (Cetacea) indicating a possible relationship between Vastan artiodactyls and basal Cetacea. [ABSTRACT FROM AUTHOR]

We present the first detailed account of cranial ontogeny in a fossil marsupial. An exceptionally well-preserved ontogenetic sample representing 26 individuals of Nimbadon lavarackorum (Diprotodontidae, Zygomaturinae) is described from a 15 million-year-old cave deposit in the Riversleigh World Heritage Area, Queensland. Based on comparison with one of N. lavarackorum's closest living relatives, the common wombat (Vombatus ursinus), the N. lavarackorum sample represents developmental stages spanning suckling pouch young through to elderly adults. In addition to documenting ontogenetic changes, reduced major axis regression analyses of 14 cranial and seven mandibular measurements were used to analyze allometric growth. Early growth patterns in the cranium are comparable to those of other marsupials such that the bones of the facial portion of the cranium develop precociously compared with those of the neurocranium. Most differences between adult and juvenile crania result from reorganization of structures associated with the cranio-mandibular joint and the developing dentition and strengthening of areas for insertion of the muscles of mastication. These changes reflect the transition from a purely suckling function to one focused on mastication of leaves. The sample also provides a unique view into the development of the extraordinarily complex endocranial sinuses characteristic of diprotodontid marsupials. [ABSTRACT FROM AUTHOR]

The article discusses the evolution of non-homologous venom delivery systems. The extratarsal spur present on the hind limb of all male monotremes has been discovered into a venom delivery system possessing the ability to produce toxic saliva compared with the isolated lower canines, a taxonomically indeterminate Paleocene mammal species which represent a plesiomorphic mammalian character. It notes that the analyses provided by the mandibular morphology that venom delivery systems evolved independently would still be a great challenge in paleobiology to provide a conclusion for the given theory. It shows that dental character ia non-homologous in the diversity of venom delivery system in mammal group proven in the study of craniodental adaptation identified in Beremendia and Dolinasorex.

Xotodon caravela, a new species of toxodontid from northwestern Argentina, is presented. The material studied consists of a well-preserved and nearly complete mandible and a maxillary fragment, recovered in the Aconquija Formation (late Miocene-early Pliocene) at the El Molino locality (Tucumán Province, Argentina). The fossil diversity of the levels is concordant with an early Pliocene fauna. The general features of the dentition and mandible (e.g., concave ectoloph and single lingual fold on upper molars, anterior fold mesially displaced relative to the hypoflexid in the lower molars, sigmoid lateral outline of chin, and continuous enamel on M3) allow the inclusion of this specimen in the genus Xotodon. In turn, some traits indicate unequivocally that this is a new species, such as the anterior region without constriction at the premolar level, the approximately 13° angle of implantation of the i3 in relation to the ventral edge of the mandibular body (without lateral divergence), and the presence of an intra-alveolar projection of the incisive crown extending laterally below the premolars to the level of the p4 and forming a robust projection or lateral ledge. The new taxon was included in a matrix of 59 characters and compared with 32 notoungulate genera. The phylogenetic position and comparative analysis support the taxonomic interpretation of the studied specimen as a new species of Xotodon. This represents the first record of a toxodontid in the Neogene lowlands of northwestern Argentina and contributes to our knowledge of this family in the region. Citation for this article: Armella, M. A., D. A. García-López, and L. Dominguez. 2018. A new species of Xotodon (Notoungulata, Toxodontidae) from northwestern Argentina. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1425882. [ABSTRACT FROM AUTHOR]

The planktivorous mobulid rays are a sister group to, and descended from, rhinopterid and myliobatid rays that possess a dentition showing adaptations consistent with a specialized durophagous diet. Within the Paleocene and Eocene, there are several taxa that display dentitions apparently transitional between these extreme trophic modalities, in particular the genusBurnhamia. The holotype ofBurnhamia daviesiwas studied through X-ray computed tomography (CT) scanning. Digital renderings of this incomplete but articulated jaw and dentition revealed previously unrecognized characters regarding the jaw cartilages and teeth. In addition, the genusSulcidens, gen. nov., is erected for articulated dentitions from the Paleocene previously assigned toMyliobatis. Phylogenetic analyses confirmBurnhamiaas a sister taxon to the mobulids and the Mobulidae as a sister group toRhinoptera. Shared dental characters betweenBurnhamiaandSulcidenslikely represent independent origins of planktivory within the rhinopterid-myliobatid clade. The transition from highly specialized durophagous feeding morphologies to the morphology of planktivores is perplexing but was facilitated by a pelagic swimming mode in these rays and, we propose, through subsequent transition from either meiofauna-feeding or pelagic fish-feeding to pelagic planktivory. http://zoobank.org/urn:lsid:zoobank.org:pub:511E9C39-1208-4F56-8DC1-2B92D2EDB4B3 Citation for this article: Underwood, C. J., M. A. Kolmann, and D. J. Ward. 2017. Paleogene origin of planktivory in the Batoidea. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1293068. [ABSTRACT FROM AUTHOR]

Computed tomographic scan data of three premaxillae, a maxilla, and a dentary ofDicraeosaurus hansemanniallow reconstruction of the tooth replacement pattern in this taxon. Four or five replacement teeth are present in each of the four tooth families of the premaxilla. The interalveolar septum is labially interrupted, and an alveolar trough is formed. In the maxilla, the number of replacement teeth decreases in a caudal direction from four to one per tooth family. The dentary bears 16 alveoli, and the number of replacement teeth decreases caudally from three to one per tooth family. Replacement rates are around 20 days for the premaxillary and rostral maxillary teeth ofDicraeosaurus, which confirms the presence of high tooth replacement rates in Diplodocoidea. Replacement teeth of the dentary are less than half as large as those of the upper jaw, and replacement rates are around 50 days for the rostral dentary teeth. Hypothetical reconstruction of Zahnreihen yields a potential z-spacing of 1 with simultaneous front-to-back tooth replacement. Most probably, the rostral-most teeth inDicraeosauruswere used for food acquisition, whereas the more caudally positioned teeth served only as a guide and as a lateral limit for the food within the mouth. The teeth of the dentary were less prone to wear than those of the upper jaws. These findings are in agreement with the reconstructions ofDicraeosaurusas a selective mid-height browser. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free atwww.tandfonline.com/UJVP Citation for this article: Schwarz, D., J. C. D. Kosch, G. Fritsch, and T. Hildebrandt. 2015. Dentition and tooth replacement ofDicraeosaurus hansemanni(Dinosauria, Sauropoda, Diplodocoidea) from the Tendaguru Formation of Tanzania. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1008134 . [ABSTRACT FROM AUTHOR]