Calcareous nannofossil biostratigraphy and paleoclimatology of the Paleocene succession,Tenida area,Western Desert,Egypt

This study is a preliminary quantitative analysis of Paleocene calcareous nannofossil assemblages of the Tenida area (Egypt) in order to establish a detailed biostratigraphic framework as well as to reconstruct the paleoclimatic trends. A total of 48 samples with an average sample spacing of 1.5 m allowed the identification of 63 calcareous nannofossil species belonging to 19 different genera. The preservation of the studied samples varies from poor to moderate and is characterized by the frequent presence of small frangible placoliths, and nannoliths. This study recognizes three calcareous nannofossil biozones in the Danian-Thanetian time interval; Chiasmolithus danicus (NP3) Zone, Ellipsolithus macellus (NP4) Zone, and Heliolithus kleinpellii (NP6) Zone. Moreover, the multivariate statistical analysis of the calcareous nannofossil communities reveals a relationship between the distribution of these nannofossil assemblages and variations in paleoclimatic trends. Accordingly, the relative abundances of Coccolithus pelagicus in addition to nine calcareous nannofossil genera along with the diversity and preservation indices of calcareous nannofossil elements have been used to elucidate changes in paleoclimatic trends. Based on the cyclic change from cold to warm climates, it was possible to subdivide the Paleocene Period recorded in the Tenida section into four paleoclimatic intervals. The oldest is a global cooling trend spanning 2.01 Myr long, starting in the early Paleocene (Danian) during the deposition of the lower part of the Kharga Shale Member. This cooling trend is followed by a ～ 0.56 Myr warming trend during deposition of the middle part of the Kharga Shale Member that was followed by a return to a cooling mode, with an estimated duration of roughly 1.67 Myr. The last interval includes a 0.39 Myr long period at the Selandian/Thanetian boundary interval, which is dominated by a global warming trend during deposition of the upper part of the Upper Kharga Shale Member.     

Age and stratigraphic reassessment of the fossil-bearing Laguna Umayo red mudstone unit, SE Peru, from regional stratigraphy, fossil record, and paleomagnetism

The thick red mudstone unit that crops out at Laguna Umayo (Puno department, southern Peru), here referred as LURMU, has yielded in different levels a fossil assemblage with plants and vertebrates (including mammals). On the basis of charophytes, the unit was initially assigned to the Vilquechico Formation (Maastrichtian-Danian), of regional extension, and the dinosaurian structure of egg fragments was interpreted as consistent with that age. Revision of the regional stratigraphy leads to reassignment of this unit to the Lower Muñani Formation (Early Tertiary). Mammals from the LU-3 and Chulpas levels present affinities with forms from the Upper Paleocene of South America (Patagonia, Brazil). A bunodont marsupial, Chulpasia, is evidence for chronologic proximity to a transantarctic interchange with Australia at the end of the Paleocene. Furthermore, magnetostratigraphy of the LURMU reveals a single reverse polarity zone of 300 m thickness. Because of the new stratigraphic and paleomammalogic data, this long reverse polarity zone is likely correlative to Chron 26r (early Late Paleocene) or Chron 24r (latest Paleocene-earliest Eocene), or, less likely, to Chron 29r (latest Cretaceous-earliest Paleocene). The arguments previously invoked in favor of a Cretaceous age (charophytes, dinosaurian eggs) are critically evaluated, and correlation to Chron 24r is favored.     

江西晚古新世南方有蹄目一新属及其有关问题讨论

本文主要记述了南方有蹄目北柱兽科一新属新种——南方沟柱兽 (Bothriostylops notios gen. et sp. nov.).化石发现于江西池江盆地晚古新世池江组.新属牙齿形态与其他已记述的北柱兽科种类均有一定的差别,但与稀少亚洲柱兽 (Asiostylops spanios) 和原"中华柱兽"进步种 ("Sinostylops" progressus) 在系统关系上比较密切.本文初步讨论了"中华柱兽"属中有关种的分类和归属问题.     

A new, nearly complete stem turtle from the Jurassic of South America with implications for turtle evolution

Turtles have been known since the Upper Triassic (210Myr old); however, fossils recording the first steps of turtle evolution are scarce and often fragmentary. As a consequence, one of the main questions is whether living turtles (Testudines) originated during the Late Triassic (210Myr old) or during the Middle to Late Jurassic (ca 160Myr old). The discovery of the new fossil turtle, Condorchelys antiqua gen. et sp. nov. from the Middle to Upper Jurassic (ca 160-146Myr old) of South America (Patagonia, Argentina), presented here sheds new light on early turtle evolution. An updated cladistic analysis of turtles shows that C. antiqua and other fossil turtles are not crown turtles, but stem turtles. This cladistic analysis also shows that stem turtles were more diverse than previously thought, and that until the Middle to Upper Jurassic there were turtles without the modern jaw closure mechanism.     

Penguin heat-retention structures evolved in a greenhouse Earth

Penguins (Sphenisciformes) inhabit some of the most extreme environments on Earth. The 60+ Myr fossil record of penguins spans an interval that witnessed dramatic shifts in Cenozoic ocean temperatures and currents, indicating a long interplay between penguin evolution and environmental change. Perhaps the most celebrated example is the successful Late Cenozoic invasion of glacial environments by crown clade penguins. A major adaptation that allows penguins to forage in cold water is the humeral arterial plexus, a vascular counter-current heat exchanger (CCHE) that limits heat loss through the flipper. Fossil evidence reveals that the humeral plexus arose at least 49 Ma during a 'Greenhouse Earth' interval. The evolution of the CCHE is therefore unrelated to global cooling or development of polar ice sheets, but probably represents an adaptation to foraging in subsurface waters at temperate latitudes. As global climate cooled, the CCHE was key to invasion of thermally more demanding environments associated with Antarctic ice sheets.     

First Clarkforkian Equivalent Land Mammal Age in the Latest Paleocene Basal Sparnacian Facies of Europe: Fauna,Flora, Paleoenvironment and (Bio)stratigraphy

The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a “miacid” carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America.     

A compsemydid turtle from the Upper Cretaceous of Var,southern France

Calissounemys matheroni gen. et sp. nov. (Testudines) is described on the basis of a skull and shell elements from the Upper Cretaceous of Var, southern France. This new taxon is assigned to the family Compsemydidae and characterized by a thick-boned, robust skull, a shallow temporal emargination, a crista supraoccipitalis not extending beyond the posterior edge of the skull roof, large nasals meeting along the midline for their full length; frontals retracted from the orbital margin, absence of a cheek emargination, a large jugal forming a substantial part of the orbital margin, absence of a secondary palate and an uneven upper triturating surface; and the shell with vertebral 1 clearly wider than vertebrals 2-3, with the lateral margins strongly divergent towards the anterior border and wider than long vertebrals 2-3. This find increases the diversity of the Late Cretaceous turtle fauna from southern France, and fills a stratigraphical gap in the fossil record of Compsemydidae between the Early Cretaceous and the Paleocene in Europe.     

Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution

Testing models of macroevolution, and especially the sufficiency of microevolutionary processes, requires good collaboration between molecular biologists and paleontologists. We report such a test for events around the Late Cretaceous by describing the earliest penguin fossils, analyzing complete mitochondrial genomes from an albatross, a petrel, and a loon, and describe the gradual decline of pterosaurs at the same time modern birds radiate. The penguin fossils comprise four naturally associated skeletons from the New Zealand Waipara Greensand, a Paleocene (early Tertiary) formation just above a well-known Cretaceous/Tertiary boundary site. The fossils, in a new genus (Waimanu), provide a lower estimate of 61-62 Ma for the divergence between penguins and other birds and thus establish a reliable calibration point for avian evolution. Combining fossil calibration points, DNA sequences, maximum likelihood, and Bayesian analysis, the penguin calibrations imply a radiation of modern (crown group) birds in the Late Cretaceous. This includes a conservative estimate that modern sea and shorebird lineages diverged at least by the Late Cretaceous about 74 +/- 3 Ma (Campanian). It is clear that modern birds from at least the latest Cretaceous lived at the same time as archaic birds including Hesperornis, Ichthyornis, and the diverse Enantiornithiformes. Pterosaurs, which also coexisted with early crown birds, show notable changes through the Late Cretaceous. There was a decrease in taxonomic diversity, and small- to medium-sized species disappeared well before the end of the Cretaceous. A simple reading of the fossil record might suggest competitive interactions with birds, but much more needs to be understood about pterosaur life histories. Additional fossils and molecular data are still required to help understand the role of biotic interactions in the evolution of Late Cretaceous birds and thus to test that the mechanisms of microevolution are sufficient to explain macroevolution.     

Palaeobotanical studies from tropical Africa: relevance to the evolution of forest, woodland and savannah biomes

Fossil plants provide data on climate, community composition and structure, all of which are relevant to the definition and recognition of biomes. Macrofossils reflect local vegetation, whereas pollen assemblages sample a larger area. The earliest solid evidence for angiosperm tropical rainforest in Africa is based primarily on Late Eocene to Late Oligocene (ca. 39-26 Myr ago) pollen assemblages from Cameroon, which are rich in forest families. Plant macrofossil assemblages from elsewhere in interior Africa for this time interval are rare, but new work at Chilga in the northwestern Ethiopian Highlands documents forest communities at 28 Myr ago. Initial results indicate botanical affinities with lowland West African forest. The earliest known woodland community in tropical Africa is dated at 46 Myr ago in northern Tanzania, as documented by leaves and fruits from lake deposits. The community around the lake was dominated by caesalpinioid legumes, but included Acacia, for which this, to my knowledge, is the earliest record. This community is structurally similar to modern miombo, although it is different at the generic level. The grass-dominated savannah biome began to expand in the Middle Miocene (16 Myr ago), and became widespread in the Late Miocene (ca. 8 Myr ago), as documented by pollen and carbon isotopes from both West and East Africa.     

Maastrichtian-early Paleocene foraminiferal palaeobathymetry and depositional sequences at Gebel El Sharawna,south Luxor,Egypt

Maastrichtian-early Paleocene foraminiferal palaeobathymetry, palaeodiversity and vertical facies changes of Gebel El Sharawna, south Luxor, Egypt have been studied to determine the depositional sequences, their relationships to global records and/or tectonic signatures. Five benthonic assemblages are recorded and replicated in the present study reflect fluctuation in palaeo-water depth from restricted marginal marine to outer shelf palaeoenvironments. Four sequence boundaries that coincide with the Campanian/Maastrichtian, intra-early Maastrichtian, Early/Late Maastrichtian, Cretaceous/Palaeogene (K/Pg) and intra-Danian were recognized based upon sharp vertical facies changes, foraminiferal assemblage changes, hiatuses, mineral hard ground and reworking. The K/Pg unconformity reveals an unexpected ca. 4.2 Myr time gap as indicated by the absence of the CF2 Zone through lower part of the P1c Zone. It is easily distinguished in the field by conglomeration and winnowing of phosphate and glauconite in the lower Paleocene. These sequence boundaries defined five third-order depositional sequences mainly developed as the result of the eustatic sea-level changes, coupled with the Arabian–Nubian shield tectonic uplift at the southern edge of the Tethys Ocean.     

A Giant Chelonioid Turtle from the Late Cretaceous of Morocco with a Suction Feeding Apparatus Unique among Tetrapods

Background

Secondary adaptation to aquatic life occurred independently in several amniote lineages, including reptiles during the Mesozoic and mammals during the Cenozoic. These evolutionary shifts to aquatic environments imply major morphological modifications, especially of the feeding apparatus. Mesozoic (250–65 Myr) marine reptiles, such as ichthyosaurs, plesiosaurs, mosasaurid squamates, crocodiles, and turtles, exhibit a wide range of adaptations to aquatic feeding and a broad overlap of their tooth morphospaces with those of Cenozoic marine mammals. However, despite these multiple feeding behavior convergences, suction feeding, though being a common feeding strategy in aquatic vertebrates and in marine mammals in particular, has been extremely rarely reported for Mesozoic marine reptiles.

Principal Findings

A relative of fossil protostegid and dermochelyoid sea turtles, Ocepechelon bouyai gen. et sp. nov. is a new giant chelonioid from the Late Maastrichtian (67 Myr) of Morocco exhibiting remarkable adaptations to marine life (among others, very dorsally and posteriorly located nostrils). The 70-cm-long skull of Ocepechelon not only makes it one of the largest marine turtles ever described, but also deviates significantly from typical turtle cranial morphology. It shares unique convergences with both syngnathid fishes (unique long tubular bony snout ending in a rounded and anteriorly directed mouth) and beaked whales (large size and elongated edentulous jaws). This striking anatomy suggests extreme adaptation for suction feeding unmatched among known turtles.

Conclusion/Significance

The feeding apparatus of Ocepechelon, a bony pipette-like snout, is unique among tetrapods. This new taxon exemplifies the successful systematic and ecological diversification of chelonioid turtles during the Late Cretaceous. This new evidence for a unique trophic specialization in turtles, along with the abundant marine vertebrate faunas associated to Ocepechelon in the Late Maastrichtian phosphatic beds of Morocco, further supports the hypothesis that marine life was, at least locally, very diversified just prior to the Cretaceous/Palaeogene (K/Pg) biotic crisis.     

Paleocene-Early Eocene ostracodes from the Southern Galala Plateau (Eastern Desert, Egypt): Taxonomy, impact of paleobathymetric changes

Ostracode faunas obtained from nine sections spanning the Paleocene-Early Eocene interval from a platform-basin transect in the Southern Galala Plateau area (Eastern Desert, Egypt) have been investigated. The study focuses on taxonomy and biostratigraphy of the ostracode assemblages across the P/E boundary, with supporting comments on paleoecology and paleobiogeography. The studied nine sections yielded 60 taxa belonging to 39 genera. Five species are new. The P/E transition is characterized by the appearance of new taxa rather than extinctions. During the Early and early Late Paleocene, the ostracode assemblages throughout the study area are largely similar, being dominated by middle-outer neritic taxa. In the late Late Paleocene and Early Eocene, changes in the paleobathymetry from deeper marine environments in the distal area in the south to shallower marine environments in the proximal area in the north become pronounced. Many of the recorded taxa have a wide geographic distribution throughout the Middle East and North Africa. Similarities with basins of West Africa are also found, reflecting faunal exchanges between this area and southern Tethys during the Paleocene and Early Eocene.     

Liverwort fossils from the Late Triassic of Baiyin City,Gansu Province,and their geological significance

Although liverworts are widely distributed around the world with a large number of extant species, reliable fossil records are relatively rare. Here, we report a new species, Ricciopsis baojishanensis Han and Yan, n. sp. (Ricciaceae) and an unnamed species, Hepaticites sp. from the Late Triassic Nanying’er Formation in Baojishan Basin, Baiyin City, Gansu Province, Northwest China. The generic designation is based on detailed comparison of the gross morphology with related fossil and extant species. The new species is characterized by its rosette-forming thallus, dichotomous branching, ribbon-like segments and entire margins. The current fossils represent the first record of liverwort from the Late Triassic in Baojishan Basin, Gansu Province. Based on the different fossil records of the Ricciaceae, we suggest that these taxa were widely distributed during Late Triassic to Oligocene worldwide, mainly in warm temperate and tropical environments, similar with their current distribution. The discovery of the present fossils indicates that the climate of Baojishan Basin in Late Triassic is warmer and more humid than that of today.     

Bone-eating Osedax worms lived on Mesozoic marine reptile deadfalls

We report fossil traces of Osedax, a genus of siboglinid annelids that consume the skeletons of sunken vertebrates on the ocean floor, from early-Late Cretaceous (approx. 100 Myr) plesiosaur and sea turtle bones. Although plesiosaurs went extinct at the end-Cretaceous mass extinction (66 Myr), chelonioids survived the event and diversified, and thus provided sustenance for Osedax in the 20 Myr gap preceding the radiation of cetaceans, their main modern food source. This finding shows that marine reptile carcasses, before whales, played a key role in the evolution and dispersal of Osedax and confirms that its generalist ability of colonizing different vertebrate substrates, like fishes and marine birds, besides whale bones, is an ancestral trait. A Cretaceous age for unequivocal Osedax trace fossils also dates back to the Mesozoic the origin of the entire siboglinid family, which includes chemosynthetic tubeworms living at hydrothermal vents and seeps, contrary to phylogenetic estimations of a Late Mesozoic–Cenozoic origin (approx. 50–100 Myr).     

Cretaceous and Cenozoic non-marine deposits of the Northern South Yellow Sea Basin, offshore western Korea: palynostratigraphy and palaeoenvironments

Palynological analyses of two wells (Haema-1 and Kachi-1) located in two sub-basins of the Northern South Yellow Sea Basin have been carried out in order to establish a palynostratigraphic breakdown of the sedimentary succession and to determine environments of deposition. Seven assemblage zones and two assemblage subzones have been erected on the basis of frequency variations in, and occurrences of, biostratigraphically significant palynomorphs as follows: Classopollis-Ephedripites Assemblage Zone (AZ): Barremian-Albian; Alisporites-Aquilapollenites-Penetetrapites AZ, which is subdivided into an Alisporites-Rugubivesiculites Assemblage Subzone: Cenomanian-Lower Maastrichtian, and an Aquilapollenites-Penetetrapites Assemblage Subzone: Upper Maastrichtian; Momipites-Coryluspollenites AZ: Paleocene; Caryapollenites-Inaperturopollenites AZ: Lower-Middle Eocene; Quercoidites-Pinuspollenites AZ: Upper Eocene; Liquidambarpollenites-Fupingopollenites-Magnastriatites AZ: Lower-Middle Miocene; Graminidites-Persicarioipollis AZ: Pliocene. The depositional environments represented by the well sections are considered to have been generally fluvio-lacustrine, and the climate to have varied between semi-arid and wet, and subtropical and warm temperate, except during the Late Eocene and Pliocene when a cool-temperate climate prevailed. Six stages in the development of the sub-basins are recognised. These are: (1) initial stage of rift or pull-apart basin-formation during the Late Jurassic?-Cretaceous; (2) subsidence from the Paleocene to Middle Eocene; (3) alternation of uplift and subsidence in the Late Eocene; (4) synrift inversion and erosion through the Oligocene; (5) uplift during the Early Miocene; and (6) widespread subsidence from the Middle Miocene onwards apart from during the Early Pliocene when the region was subjected to uplift once more.     

The Inner Ear of Two Late Cretaceous Multituberculate Mammals, and Its Implications for Multituberculate Hearing

The inner ear of the Late Cretaceous multituberculates Nemegtbaatar gobiensis and Chulsan-baatar vulgaris is described from serial sections and enlarged models. The size and proportions of the inner ear as a whole are as expected for extant small mammals. The lengths of the cochlea (Nemegtbaatar gobiensis, 3.0 mm, Chulsanbaatar vulgaris, 2.0 mm) are comparable to those of other multituberculates, when ratios of length of the cochlea to skull length are calculated. The vestibule is not as expanded in the two taxa as in Lambdopsalis, ?Meniscoessus, and ?Catopsalis; the estimated volume for Nemegtbaatar gobiensis is 9 mm³. A slightly laterally curved, anteriomedially directed cochlea, relatively robust ear ossicles, and the estimations of the area of the tympanic membrane and stapedial footplate in Chulsanbaatar suggest high-frequency hearing but a relatively low sensitivity to low-decibel sounds. The semicircular canals of Nemegtbaatar and Chulsanbaatar are fully developed; the size of the anterior, posterior, and lateral canals and their angles and proportions are comparable to those of extant mammals of similar size. The anterior semicircular canal of Nemegtbaatar forms a smooth half-circle and thus is more derived than the angular canal of Ornithorhynchus. The notable differences between the ratio of the width of the lateral semicircular canal to skull length and the size of the vestibule in Nemegtbaatar and the Paleocene multituberculate Lambdopsalis bulla are probably related to different modes of life.     

Microfacies and sequence stratigraphy of the Amapá Formation, Late Paleocene to Early Eocene, Foz do Amazonas Basin, Brazil

On the basis of thin-section studies of cuttings and a core from two wells in the Amapá Formation of the Foz do Amazonas Basin, five main microfacies have been recognized within three stratigraphic sequences deposited during the Late Paleocene to Early Eocene. The facies are: 1) Ranikothalia grainstone to packstone facies; 2) ooidal grainstone to packstone facies; 3) larger foraminiferal and red algal grainstone to packstone facies; 4) Amphistegina and Helicostegina packstone facies; and 5) green algal and small benthic foraminiferal grainstone to packstone facies, divisible locally into a green algal and the miliolid foraminiferal subfacies and a green algal and small rotaliine foraminiferal subfacies. The lowermost sequence (S1) was deposited in the Late Paleocene–Early Eocene (biozone LF1, equivalent to P3–P6?) and includes rudaceous grainstones and packstones with large specimens of Ranikothalia bermudezi representative of the mid- and inner ramp. The intermediate and uppermost sequences (S2 and S3) display well-developed lowstand deposits formed at the end of the Late Paleocene (upper biozone LF1) and beginning of the Early Eocene (biozone LF2) on the inner ramp (larger foraminiferal and red algal grainstone to packstone facies), in lagoons (green algal and small benthic foraminiferal facies) and as shoals (ooidal facies) or banks (Amphistegina and Helicostegina facies). Depth and oceanic influence were the main controls on the distribution of these microfacies. Stratal stacking patterns evident within these sequences may well have been related to sea level changes postulated for the Late Paleocene and Early Eocene. During this time, the Amapá Formation was dominated by cyclic sedimentation on a gently sloping ramp. Environmental and ecological stress brought about by sea level change at the end of the biozone LF1 led to the extinction of the larger foraminifera (Ranikothalia bermudezi).     

Agaristoxylon garennicum Gerrienne et al., gen. et sp. nov., an arborescent Ericaceae from the Belgian Upper Paleocene: palaeoenvironmental implications

This paper describes a silicified trunk fragment, Agaristoxylon garennicum Gerrienne et al., gen. et sp. nov., collected from a new locality at Péruwelz (Belgium) in the marine Thanetian (Upper Paleocene), and discusses the fossilisation conditions of the specimen. The anatomical structure of Agaristoxylon is similar to that of the modern ericaceous genus Agarista (Agauria), encountered in the tropical and subtropical North and South America, and in the tropical regions of Africa, Madagascar and the Mascarene Islands. Together with other palaeontological data, the presence of Agaristoxylon supports the hypothesis that a climate of subtropical type with high atmospheric humidity could have prevailed in Belgium, at least locally, during the Late Paleocene. The occurrence of indistinct growth rings suggests the existence of seasonal drier periods.     

New records of archaic ungulates from the Lower Eocene of Sanshui Basin,Guangdong, China

Phenacolophidae is a group of little known archaic ungulates from the Late Paleocene to Middle Eocene of Asia. Its phylogenetic relationships with other altungulates have remained uncertain, partly because most phenacolophids are represented by poorly preserved material. Here we report a new phenacolophid, Sanshuilophus zhaoi gen. et sp. nov., from the Lower Eocene Huayong Formation of the Sanshui Basin, Guangdong, China. Although still fragmentary, the new specimens show that the new taxon is characterised by relatively large body size (except for Zaisanolophus), sub-molariform premolars, relatively higher bilophodont molars that lack the mesostyle, and tooth enamel microstructure with true prisms and typical Hunter-Schreger bands (HSB). With the new specimens and a review of the published phenacolophid material, we are able to provide an alternative identification for the tooth loci for the type specimen of Phenacolophus and further present an emended diagnosis for Phenacolophidae. The tooth morphology and enamel microstructure provide new evidence to support the notion that phenacolophids differ from species of Embrithopoda in having low-crown teeth, considerably slanting lophids, distinct paralophids and lacking the arsinoitheriid radial enamel. Phenacolophidae should not be included in Tethytheria but probably represent a stem group for altungulates, if not for all archaic ungulates.