Lingual Cingulum Research Articles

A new early-diverging probainognathian cynodont and a revision of the occurrence of cf. Aleodon from the Chañares Formation, northwestern Argentina: New clues on the faunistic composition of the latest Middle-?earliest Late Triassic Tarjadia Assemblage Zone.

The Chañares Formation (Ischigualasto-Villa Unión Basin) is worldwide known by its exquisitely preserved fossil record of latest Middle-to-early Late Triassic tetrapods, including erpetosuchids, "rauisuchians," proterochampsids, gracilisuchids, dinosauromorphs, pterosauromorphs, kannemeyeriiform dicynodonts, and traversodontid, chiniquodontid and probainognathid cynodonts, coming from the Tarjadia (bottom) and Massetognathus-Chanaresuchus (top) Assemblage Zones of its lower member. Regarding cynodonts, most of its profuse knowledge comes from the traditional layers discovered by Alfred Romer and his team in the 1960s that are now enclosed in the Massetognathus-Chanaresuchus Assemblage Zone (AZ). In this contribution we focus our study on the probainognathian cynodonts discovered in levels of the Tarjadia Assemblage Zone. We describe a new chiniquodontid cynodont with transversely broad postcanine teeth (Riojanodon nenoi gen. et sp. nov.) which is related to the genus Aleodon. In addition, the specimen CRILAR-Pv 567 previously referred to cf. Aleodon is here described, compared, and included in a phylogenetic analysis. It is considered as an indeterminate Aleodontinae nov., a clade here proposed to included chiniquodontids with transversely broad upper and lower postcanines, by having a cuspidated sectorial labial margin and a lingual platform that is twice broader than a lingual cingulum. Cromptodon mamiferoides, from the Cerro de Las Cabras Formation (Cuyo Basin), was also included in the phylogenetic analysis and recovered as an Aleodontinae. The new cynodont and the record of Aleodontinae indet. reinforce the faunal differentiation between the Tarjadia and Massetognathus-Chanaresuchus Assemblage Zones, in the lower member of the Chañares Formation, and inform on the diverse chiniquodontid clade with both sectorial and transversely broad postcanine teeth.

Early Miocene Aprotodon (Perissodactyla, Rhinocerotidae) from Northern China

ABSTRACT The genus Aprotodon is a special group of rhinoceroses, which has a very long survival time frame but a relatively limited distribution in Asia. Herein, we report on a well-preserved and complete skull found in the lower layers of the Zhang’enbao Formation from the Early Miocene age in Tongxin County, China. The morphology of the new specimen is different from all the known species of Aprotodon in its smaller size, with both sides of the parietal crest fused and forming a sagittal crest, the V-shaped anterior edge of the posterior nares positioned at the level of M2, the weak supraorbital tuberosity, the developed and multiple crista on premolars, and the reduced lingual cingulum, forming a pillar around the entrance of the medisinus on molars. Based on these, we refer the Tongxin specimen to a new species, A. qiui sp. nov. Phylogenetic analysis reveals that A. qiui sp. nov. and other members of Aprotodon are in a stable monophyletic clade. A. qiui sp. nov. is the sister taxon to A. lanzhouensis.

The first eutriconodontan mammal from the Cretaceous (Maastrichtian) of India

ABSTRACT Eutriconodonta is a diverse group of crown mammals that are known from the Jurassic and Cretaceous, mainly on the northern landmasses. Here we report a single lower molariform from the “intertrappean” deposits exposed near Anjar, in the Kutch district of the state of Gujarat, India that date to the last 259,000 years of the Cretaceous. The lower molariform of this new genus of eutriconodontan is relatively large, has three subequal, erect, lanceolated cusps, and lacks both a buccal and lingual cingulum, accessory cusps (d, e), and a vertical groove mesial to cusp b. It represents the first eutriconodontan mammal from the Cretaceous of India and the Late Cretaceous of Gondwana, and is the globally youngest record of this group. The results of a cladistic analysis support placement of the new Indian taxon among the Eutriconodonta, possibly more closely allied to triconodontids than to other groups. This new genus of eutriconodontan is the tenth named mammalian species known from the Late Cretaceous of India and the first relatively large-bodied faunivore. This record shows that the Eutriconodonta had a broader temporal and geographic distribution than previously thought and highlights the importance of continued paleontological exploration on the Indian subcontinent. http://zoobank.org/urn:lsid:zoobank.org:pub:84D96471-E733-420B-9FA2-F41BC4B62E4B

Middle Pleistocene Pongo from Ganxian Cave in southern China with implications for understanding dental size evolution in orangutans

The Pongo fossil record of China extends from the Early Pleistocene to the Late Pleistocene, but to date, no late Middle Pleistocene samples of Pongo with precise absolute dating have been identified in southern China. Here, we report the recovery of 106 fossil teeth of Pongo from Ganxian Cave in the Bubing Basin, Guangxi, southern China. We dated the speleothems using Uranium-series and dated the two rhinoceros teeth using coupled electron spin resonance/Uranium-series dating methods to between 168.9 ± 2.4 ka and 362 ± 78 ka, respectively. These dates are consistent with the biostratigraphic and magnetostratigraphic age estimates. We further describe the fossil teeth from Ganxian Cave and compare them metrically to samples of fossil Pongo (i.e., Pongo weidenreichi, Pongo duboisi, Pongo palaeosumatrensis, Pongo javensis, and Pongo sp.) from the Early, Middle, and Late Pleistocene and to extant Pongo (i.e., Pongo pygmaeus and Pongo abelii) from Southeast Asia. Based on overall dental size, a high frequency of lingual cingulum remnants on the upper molars, and a low frequency of moderate to heavy wrinkling on the molars, we attribute the Ganxian fossils to P. weidenreichi. Compared with Pongo fossils from other mainland Southeast Asia sites, those from Ganxian confirm that dental size reduction of Pongo occurred principally during the Early and Middle Pleistocene. From the Middle to Late Pleistocene, all teeth except the P3 show little change in occlusal area, indicating that the size of these teeth remained relatively stable over time. The evolutionary trajectory of the Pongo dentition through time may be more complex than previously thought. More orangutan fossils with precise dating constraints are the keys to solving this issue.

Taxonomy and phylogeny of the smallest Miocene rhinocerotid Parvorhinus n. gen. (Mammalia, Rhinocerotidae)

Middle Miocene Rhinocerotini are particularly important to understand the origin and evolution of latest Miocene and then Plio-Pleistocene taxa. However, little is known about some early divergent Rhinocerotina such as ‘Dicerorhinus’ steinheimensis. A sample of a small-sized rhinocerotid from the Middle Miocene (Mammal Neogene Zone 6) locality of Devínska Nová Ves (Bratislava, Slovakia) is here described for the first time. The specimens consist of maxillae, fragment of mandibles and postcranial remains. The described specimens clearly differ from Middle Miocene representatives of elasmotheres, aceratheres and brachypotheres, but closely resemble the poorly known rhinocerotid ‘Dicerorhinus’ steinheimensis. A cladistic analysis shows that this taxon is related with the early divergent Rhinocerotina, such as Lartetotherium sansaniense and Gaindatherium browni, and it is distantly related with both Rhinoceros and Dicerorhinus. Considering the position and the peculiar morphological and morphometric features, such as smaller size with respect to other Rhinocerotini species, posterior border of the symphysis in front of p2, crochet always present on P2-P4, P1 always absent, protoloph interrupted on P2, lingual cingulum absent on M1-M2, posterior part of the ectoloph concave on M1-M2, ‘Dicerorhinus’ steinheimensis is here included in the new genus Parvorhinus.

New cynodonts (Therapsida, Eucynodontia) from the Late Triassic of India and their significances

AbstractThe Upper Triassic Tiki Formation of India has yielded several new cynodont taxa, which are described on the basis of multiple isolated teeth and a jaw fragment. A new species of dromatheriid,Rewaconodon indicus, is defined by a tri- and tetracuspid asymmetric crown, long anterior edge of the major cuspa, cingular cuspsdandf, and marked constriction at the crown-root junction. Another new dromatheriid,Inditherium florisn. gen. n. sp., is characterized by a broad, flower-shaped pentacuspid crown, multiple cingular cusps, and a weak lingual cingulum is also described from the same horizon. In addition, a new mammaliamorph taxon,Tikiodon cromptonin. gen. n. sp., is established on a tooth specimen, which has a shovel-shaped crown, three closely spaced main cusps, a pronounced lingual cingulum with multiple cingular cusps, and a root of incomplete root bifurcation. Such a tooth morphology occupies an intermediate position between the non-mammalian cynodonts and the early mammals, as is evident from the co-occurrence of various cynodont dental morphotypes in the Tiki Formation. Moreover, Late Triassic cynodonts occurred along narrow belts demarcated by paleolatitudes, though the Indian fauna shows both Laurasian and Gondwanan affinities.UUID:http://zoobank.org/c2c575ad-ee23-4f33-8a30-661c548a5b17

A New Prozostrodontian Cynodont (Eucynodontia, Probainognathia) from the Upper Triassic of Southern Brazil

ABSTRACT Probainognathian cynodonts are well represented in the fossil record from the Middle and Upper Triassic of South America, especially in Brazil and Argentina. In this contribution, we describe a new genus and species of non-mammaliaform prozostrodontian cynodont from southern Brazil. The new taxon comes from the Niemeyer Site, a locality in which the traversodontid cynodont Siriusgnathus niemeyerorum is numerically dominant, whereas probainognathians and other tetrapods are comparatively scarce. The fauna from the Niemeyer Site was putatively assigned to the Riograndia Assemblage Zone (Norian age) recently, although none of the index fossils for that biozone (e.g., Riograndia, Clevosaurus, Jachaleria) have so far been discovered at this locality. The new cynodont taxon is based on a left lower jaw with the canine and six (pc2–pc7) well-preserved postcanines (CAPPA/UFSM 0262, holotype), and a second referred specimen (CAPPA/UFSM 0208, paratype), which includes a right lower jaw with incisors, canine, and seven (pc1–pc7) postcanines, with pc6–pc7 being the best preserved. These specimens have a robust dentary, a long and dorsoventrally tall Meckelian groove, unserrated canines, and unserrated, sectorial postcanine teeth with posteriorly inclined cusps and a poorly developed lingual cingulum. This combination of features is unknown in other Carnian and Norian non-mammaliaform cynodonts. The new taxon contributes to our knowledge of the evolutionary radiation of small prozostrodonts that occurred in western Gondwana during the Late Triassic and led to the emergence of several important cynodont groups, including Mammaliaformes. http://zoobank.org/urn:lsid:zoobank.org:pub:FDC21881-532B-490A-96A1-A65EA5F62737

A comparative evaluation of the effect of different access cavity designs on root canal instrumentation efficacy and resistance to fracture assessed on maxillary central incisors: An in vitro study.

Aim:The purpose of this study is to evaluate and compare the effect of different access cavity designs on root canal instrumentation efficacy using micro-computed tomography (CT) scan and resistance to fracture evaluated using the universal testing machine on maxillary central incisor.Materials and Methodology:Forty extracted human permanent maxillary central incisors were divided into four groups for each access cavity. The access cavities were prepared according to predefined criteria and were further assessed under Micro-CT to evaluate pre and postoperative instrumentation efficacy. After biomechanical preparation and obturation, the teeth were wrapped with tin foil to maintain a thickness of 0.2–0.3 mm as periodontal ligament. Then, the silicon impression material was applied in the acrylic alveolus, to maintain and simulate the thickness of periodontal ligament and fracture resistance was checked using the universal testing machine.Statistical Analysis:Data were analyzed using one-way analysis of variance test. Pair-wise comparison was made using post hoc multiple comparison (Tukey) test.Results:Fracture resistance was highest (1272 N) for the control group followed by the Lingual Conventional Access Group (1153.90 N). Fracture resistance for Lingual Cingulum Access Group was 1130.70 N and least for the Lingual Incisal Straight-Line Access Group (1022.80 N). This difference in fracture resistance among all the groups was significant (P = 0.001). Overall comparison showed that dentin volume reduction (DVR) for Group II was 22.45 mm3, for Group III was 17.37 mm3 and for Group IV was 28. 41 mm3. This difference in DVR among the three groups was significant (P = 0.001).Conclusion:The most effective instrumentation efficacy was obtained in lingual incisal straight-line access group, followed by lingual cingulum access group, followed by lingual conventional access group. The most effective fracture resistance was obtained in the lingual conventional access group, followed by the lingual cingulum access group, followed by the lingual incisal straight-line access group.

Filling a gap in the proboscidean fossil record: a new genus from the Lutetian of Senegal

AbstractA long hiatus encompassing most of the Eocene (end of the Ypresian to the early Priabonian) breaks up the proboscidean evolutionary history, which is otherwise documented by a rich fossil record. Only two post-Ypresian localities from West Africa (Mali and Senegal) have yielded scarceMoeritherium-like dental remains. Here, we study one of these remains from Senegal and name a new genus and species,Saloumia gorodiskii. This taxon, confidently mid-Lutetian in age, evokesMoeritheriumand elephantiforms with its wrinkled enamel, lack of centrocrista, and strong lingual cingulum. However, due to its pronounced bunodonty, which departs from the bunolophodonty of bothMoeritheriumand elephantiforms, we cannot exclude the possibility thatSaloumiadocuments an early experiment in dental diversity among Paleocene–Eocene proboscideans, without direct relationships with later proboscideans.UUID:http://www.zoobank.org/0b6b83f8-817d-498c-a672-8ffa8f81a978

New material of Gobicyon (Carnivora, Amphicyonidae, Haplocyoninae) from northern China and a review of Aktaucyonini evolution

AbstractThe aberrant carnivore Gobicyon has been known for more than 80 years, but the evolutionary position and taxonomic diversity of this animal remain unclear due to the paucity of the known fossils. Here, we report a much richer and better preserved assemblage of Gobicyon material from the Tongxin and Hezheng areas, northern China. Two new species, Gobicyon yei sp. nov. from the early middle Miocene in Tongxin and Gobicyon acutus sp. nov. from the late middle Miocene in Hezheng are recognized. Much better material of Gobicyon macrognathus and one isolated tooth of Gobicyon zhegalloi from Tongxin are also described in detail. Gobicyon is recognized as a derived haplocyonid. A phylogenetic analysis of Gobicyon and related taxa has been performed for the first time. The phylogenetic tree suggests a close relationship of Aktaucyon and Gobicyon (Aktaucyonini). Among the taxa traditionally included in haplocyonids, Haplocyonopsis is the closest to Aktaucyonini, as supported by its centrally located M1 protocone and a uniformly distributed M1 lingual cingulum. The most significant evolutionary trends of Gobicyon are the reduction of the posterior molars (M2 and M3) and the strengthening of P4 and M1, suggesting a forward shift of crushing function along the tooth row.

New species of Ballusia Ginsburg and Morales, 1998 (Ursidae, Carnivora) from Miocene of Eastern Siberia, Russia

ABSTRACT The new basal ursine bear, Ballusia zhegalloi n. sp., is described from the Early Miocene Tagay 1 locality (Baikal region, Russia) based on isolated M1. Previously described maxillary fragment with M1-2 from the closely synchronous fauna of Khirgis-Nur I in Mongolia, originally referred to Ballusia elemensis, is here included into the new species. The M1 of the new species shares similarities with M1 of previously known Early Miocene European species B. elmensis but is more derived in lower medial cusps, transversally closer spaced medial ridge and lingual cingulum, and by a slightly expressed antero-external angle. The new Asian species shares some derived features with Ballusia orientalis from Early Miocene of China, such as a more rounded M1 outline, and incipient buccal styles in M1. The other characters in the two forms of Asian Ballusia imply their parallel evolution. The Tagay find represents the first record of the genus Ballusia in Russia. It elucidates phyletic affinities of early ursine bears and refines the geographic and stratigraphic range of the genus Ballusia.

A dwarf walrus from the Miocene of Baja California Sur, Mexico

Here, we describe the odobenid Nanodobenus arandai gen. et sp. nov., based on a nearly complete left mandible from the mid to late Miocene Tortugas Formation in Baja California Sur. Nanodobenus is distinguished among odobenids by displaying a unique combination of plesiomorphic and derived characters, such as narrow mandibular symphysis, well-developed genial tuberosity, bilobed canine and p2 roots, bulbous post-canine teeth with the paraconid, protoconid and hypoconid, and smooth lingual cingula. Moreover, it is characterized by its small adult body length, which is estimated at about 1.65 m. Throughout the Miocene–Pliocene odobenids are characterized by an increase in body size, especially after the extinction of desmatophocids in the late Miocene. The small size of Nanodobenus departs from this trend, demonstrating that there was greater size disparity among odobenids in the mid–late Miocene than previously thought. It is hypothesized that Nanodobenus occupied a niche that was later on occupied by similar-sized otariids, such as Thalassoleon mexicanus, which occurs sympatrically with large odobenids in the overlying Almejas Formation.

Prozostrodon brasiliensis, a probainognathian cynodont from the Late Triassic of Brazil: second record and improvements on its dental anatomy

Probainognathian cynodonts are conspicuous elements of the Assemblage Zones of the Triassic Santa Maria Supersequence in southern Brazil. Within this group, the derived clade Prozostrodontia, in which the crown group Mammalia is included, is taxonomic diverse in the Hyperodapedon and Riograndia AZs. We describe here the second known specimen (CAPPA/UFSM 0123) of Prozostrodon brasiliensis, until now only represented by its holotype. CAPPA/UFSM 0123 includes a right dentary with dentition. As in the holotype of P. brasiliensis, it has four lower incisors, pc4 with conspicuous cusp a, and small cusps b, c, and d, pc5-pc6 of ‘triconodont’ type with cusps a > c > b > d, with continuous lingual cingulum bearing up to six small discrete cusps, length of the lower tooth row more than half the length of the dentary, and relatively deep horizontal ramus of the dentary. The new specimen is about 25% smaller than the holotype and there is not a diastema between the canine and postcanine teeth, indicating its juvenile condition. Based on both known specimens of P. brasiliensis, a discussion on tooth replacement is presented, showing that the adult individual has more postcanine tooth morphotypes than the juvenile one.

New species ofPostcopemys(Cricetidae: Rodentia) from the early Pliocene of Lago de Chapala, Jalisco, Mexico

Abstract We describe a new species of cricetid rodent based on isolated molars recovered from the early Pliocene (early Blancan) Chapala Formation, Jalisco, Mexico. Compared with other named species of the genus, the new species is characterized by its large size, M1 with the median mure connected to the protocone; m1 with (1) a wide and strongly bilobed procingulum, (2) an ectolophid and ectostylid, and (3) a well-developed mesolophid on m1, but a short mesolophid in m2 not extending to the lingual cingulum. A preliminary phylogenetic analysis places the new species with other Postcopemys species from southwestern North America and with Jacobsomys dailyi. The new species comprises the second fossil record of the genus Postcopemys in Mexico and the southernmost record of the genus in North America. We refer the recently named J. dailyi to the genus Postcopemys.

Ganguroo robustiter, sp. nov. (Macropodoidea, Marsupialia), a middle to early late Miocene basal macropodid from Riversleigh World Heritage Area, Australia

ABSTRACT——Cranial and dental remains of the middle to early late Miocene macropodid kangaroo, Ganguroo robustiter, sp. nov., are described. Postcranial remains of G. robustiter were previously described as referable to G. bilamina. Ganguroo robustiter is more robust (approximately 20% larger) and more derived than G. bilamina and G. bites, in having a larger m4, a well-developed posterolingual ridge and lingual cingulum on P3, a longer P3/p3, and no stylar cusp C on M3–M4. We used previously published data matrices to analyze the phylogenetic relationship of G. robustiter. Both phylogenetic analyses, using craniodental and postcranial characters, place G. robustiter within Macropodidae, as the sister taxon to sthenurines and macropodines. Species of Ganguroo are not found to be monophyletic despite their extreme similarity in character scores. This may be due to the large amount of missing data for G. bilamina and G. bites for which no postcranial remains have been identified. Phylogenetic results are ambiguous, recovering unresolved trees with low bootstrap values, but the generic assignment of these taxa is maintained because they are remarkably similar. Species of Ganguroo may represent a phyletic lineage, with species increasing in size and losing cusp/cuspids on their premolars through time, which appears to coincide with a broader record of changing vegetation and climates through the middle Miocene.http://zoobank.org/urn:lsid:zoobank.org:pub:D0B542BE-C673-4260-8381-8B163A35AC36SUPPLEMENTAL DATA——Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Molar morphology and the expression of Carabelli's trait in 45,X females.

The purpose of this study was to observe the expression of Carabelli's trait in maxillary first (M1) and second (M2) permanent molars in relation to tooth crown size and cusp number and to consider the role of the shortage of sex chromosome material in these features during tooth crown development. The data were derived from dental casts belonging to the KVANTTI Research Project on sex chromosome abnormalities headed by Professor Lassi Alvesalo in Finland. The subjects comprised 86 45,X females, 51 first-degree female relatives, and 150 population control females. Carabelli's trait was divided into three grades and cusp number was classified into two classes in Dahlberg's P12 and P9. The tooth crown diameters were measured with a sliding digital caliper. M1 in the 45,X females expressed a lower frequency of Carabelli's trait (19.8%) than in the female relatives (37.2%, P < 0.05). There was also a higher frequency of the three-cusp pattern (11.1%) than in the female relatives (2.4%, P = 0.055) or the control females (1.3%, P < 0.001). The expression of Carabelli's trait in M2 was of the same magnitude in the 45,X females and normal controls and was related to tooth crown size, whereas its expression in M1 of the 45,X females was associated with the cusp number rather than the tooth crown size. The shortage of one X chromosome in females has an influence on the morphology of the lingual cingulum region of the maxillary first permanent molar during tooth crown development.

Description of a new species of Sparassocynus (Marsupialia: Didelphoidea: Sparassocynidae) from the late Miocene of Jujuy (Argentina) and taxonomic review of Sparassocynus heterotopicus from the Pliocene of Bolivia.

A new species of sparassocynid marsupial, Sparassocynus maimarai n. sp. from the late Miocene of Maimará Formation (Jujuy Province, Argentina) is described from a left mandibular fragment with a complete p2-m4 series. It differs from the remaining species of the genus S. bahiai (Montehermosan-late Miocene/early Pliocene-of Buenos Aires Province, Argentina) and S. derivatus (Chapadmalalan and Marplatan-Pliocene of Buenos Aires Province) by its smaller size, the relatively longer m1 with respect to the m4, the presence of a lingual cingulum extended between para- and metaconid on the m1-3, and its more robust entoconids. As part of this study the taxonomic status of Sparassocynus heterotopicus (Montehermosan, Umala, Bolivia; Pliocene) was reviewed concluding that this taxon should be referred to as 'Sparassocynus' heterotopicus and considered a Didelphoidea of uncertain affinities. Sparassocynus maimarai n. sp. is the oldest records of the genus, adding new information to evaluate the origins and early diversification of sparassocynids. Sparassocynus maimarai n. sp. was recovered with precise stratigraphic control, highlighting its potential biostratigraphic significance to the temporal correlations between Maimará Formation and other Mio-Pliocene stratigraphic units from the northwestern Argentina.

A new hornless rhinoceros of the genus Acerorhinus (Perissodactyla: Rhinocerotidae) from the Upper Miocene of Kerassiá (Euboea, Greece), with a revision of related forms

The Late Miocene locality of Kerassia (North Euboea, Greece) has yielded a rich Turolian fauna, which forms part of the Eastern Mediterranean Pikermian biome. A prominent specimen of the Kerassia collection, a well-preserved rhinocerotid skull with associated mandible, is described herein. The specimen demonstrates the diagnostic cranial, mandibular, and dental characters of the genus Acerorhinus, but it is distinct enough in several anatomical aspects from the known samples of this genus to justify the establishment of a new species, A. neleus. It is characterised by the absence of horns, dolichocephaly, a moderately concave dorsal cranial profile, closely converging parietal crests, a relatively high-positioned orbit, a markedly robust zygomatic arch, a bell-shaped occipital outline, and a robust mandible. Its strong but relatively narrow mandibular symphysis has a short diastema, a concave ventral surface, and bears a pair of moderate-sized second lower incisors suggesting a female individual. The salient features of the upper dentition include a proportionally long premolar section and traces of a thin cement coating on the labial wall of the ectolophs. The upper premolars are characterised by the presence of a faint protocone constriction and a strong lingual cingulum, whereas the upper molars by the absence of lingual cinguli and the presence of a moderate protocone constriction. Clusters of numerous borings on the specimen’s surface were attributed to bioerosion induced by dermestid beetle activity. The Kerassia specimen is closely related to the few known aceratheriine specimens from Pikermi and Chomateri, which are described and referred to A. neleus n. sp. The taxonomic relationships among certain Eurasian aceratheriine samples are discussed and an updated systematic list of the Acerorhinus species is provided.

A juvenile skull of Acerorhinus yuanmouensis (Mammalia: Rhinocerotidae) from the Late Miocene hominoid fauna of the Yuanmou Basin (Yunnan, China)

A unique juvenile skull bearing both milk premolars and unerupted but fully developed permanent premolars and molars (observed using X-ray microcomputed tomography), and some isolated upper cheek teeth, all from the Late Miocene hominoid fauna of the Yuanmou Basin (Yunnan, China), closely resemble craniodental material of Acerorhinus yuanmouensisZong, 1998 from the same locality, and are referred to this species. A phylogenetic analysis based on 214 craniodental morphological characters scored for 31 terminal taxa reveals that A. yuanmouensis should be assigned to the genus Acerorhinus indeed. The newly discovered specimens improve our understanding of this species, especially with respect to the morphology of the milk premolars and premolars. Two intraspecific variations in the upper premolars are noted: a lingual bridge may be present or absent, and the lingual cingulum continuous or reduced. The analysis also indicates that: the phylogenetic status of Acerorhinus lufengensis Deng and Qi, 2009 should be reconsidered; “Aceratherium” huadeensisQiu, 1979 does neither belong to Aceratherium nor Acerorhinus, and its phylogenetic status remains debatable.

First record of an upper deciduous molar in Desmanella (Uropsilinae, Talpidae, Mammalia)

The dP4 of Desmanella engesseriZiegler, 1985 from a maxillary which includes the P2 and P3 in crypt, the P4 in eruption and fully erupted dP4 and M1, is described from Petersbuch 28 (Germany; Lower Miocene, MN3/4). The maxillary was studied using X-ray microtomography to make detailed images of the internal and external features of the sample. This is the first record of a dP4 from DesmanellaEngesser, 1972. Its shape is unique for fossil talpids, possessing the apomorphic feature of replacing the protocone with a large lingual cingulum. The functional use of deciduous teeth and the process that led to the complete loss of milk teeth in extant talpids are discussed.