The new issue of Palaeontologia Polonica is open access and includes a number of new Mesozoic mammals.
Averianov, A.O. and Archibald, D. (2016)
New evidence on the stem placental mammal Paranyctoides from the Upper Cretaceous of Uzbekistan.
Palaeontologia Polonica 67: 25–33.
A newly discovered maxillary fragment (ZIN 102716) of Paranyctoides quadrans from the Bissekty Formation (Upper Cretaceous, Turonian) at Dzharakuduk, Uzbekistan shows this species has a P5 about half the labiolingual width of M1 and an infraorbital foramen placed above P4 near the anterior margin of the orbit and below the maxillolacrimal contact. The maxillary foramen, likely posterior to M1, is positioned more posteriorly compared to other stem placental mammals. The infraorbital canal is roofed by a thin plate of maxilla with facets for the lacrimal and jugal above. The posterior part of this roof may be formed entirely by the lacrimal. In Paranyctoides the upper posterior premolars (P4–5) and molars were confined to the posterior third of the maxilla below the orbit, as in the stem therian Eomaia. In a majority of stem placentals, including Early Cretaceous Prokennalestes and Acristatherium, the upper posterior premolars and molars occupy the posterior half of the maxilla, with P4–5 placed in front of the orbit. A new phylogenetic analysis places Paranyctoides in a polytomy with Sheikhdzheilia, Lainodon, and Zhelestinae.
Butler, P.M. and Sigogneau-Russell, D. (2016)
Diversity of triconodonts in the Middle Jurassic of Great Britain.
Palaeontologia Polonica 67: 35–65.
: pub: C4D90BB6-A001-4DDB-890E-2061B4793992
We describe a range of triconodont mammalian teeth from the Forest Marble (Middle Jurassic) of Kirtlington Quarry (Oxfordshire), Watton Cliff, and Swyre (both Dorset), and demonstrate the presence of a variety of morganucodontans, including Morganucodon tardus sp. n., Cherwellia leei gen. et sp. n., and Stylidens hookeri gen. et sp. n. “Amphilestidae” are represented by three species, Phascolotherium simpsoni sp. n., P. cf. bucklandi, and Amphilestes cf. A. broderipii, as well as by upper molars referable to Phascolotherium. Gobiconodontidae and Triconodontidae are represented by, respectively, Gobiconodon bathoniensis sp. n., and Eotriconodon sophron gen. et sp. n. Key words: “Amphilestids”, Bathonian, gobiconodontids, morganucodontids
Cifelli, R.L., Cohen, J.E., and Davis, B.M. (2016)
New tribosphenic mammals from the Mussentuchit Local Fauna (Cedar Mountain Formation, Cenomanian), Utah, USA.
Palaeontologia Polonica 67: 67–81.
LSID urn:lsid:zoobank.org:pub:C7A0F8DD-F04A- 467C-8E45-3BFABDEEC6F5
Herein we describe two new tribosphenic mammals from the Cedar Mountain Formation of Emery County, Utah, USA. The fossils occur in a narrow stratigraphic interval near the top of the unit (Mussentuchit Member) and date to approximately the Early–Late Cretaceous boundary (early Cenomanian, ~97 Mya). The specimens were recovered from screen-washing bulk rock samples. Both taxa are based on isolated teeth; from the limited morphology represented, both lack obvious specializations of the two major therian groups, Metatheria and Eutheria, and for present purposes they are regarded as basal tribosphenidans. Dakotadens pertritus sp. n. is the more abundant of the two and is closely related to a previously known species from the overlying (upper Cenomanian) Naturita Formation. Culicolestes kielanae gen. et sp. n. is notable in its large size (similar to Pariadens mckennai from the same fauna) relative to most other pre-Campanian tribosphenidans. The mammals of the Mussentuchit Local Fauna, now fully described on the basis of available fossils, represent one of the most diverse assemblages known from the Mesozoic, including some 22 taxa. Tribosphenidans, however, are neither abundant nor diverse, and include only six recognized species; most Late Cretaceous assemblages of North America include twice as many. Four of these are marsupialiforms and the remaining two, described herein, are considered basal tribosphenidans. Both eutherians and deltatheroidans, known from earlier and later faunas on the continent, are lacking. Triconodontids (Eutriconodonta) and spalacotheriids (basal Trechnotheria) make up nearly a third of mammalian diversity in the Mussentuchit Local Fauna, and account for about 40% of mammalian fossils identified to species level. Spalacotheriids (four taxa) are particularly abundant relative to both older (Albian) and younger (late Cenomanian onward) assemblages, suggesting some taphonomic or paleoecologic bias.
Davis, B.M., Cifelli, R.L., and Cohen, J.E. (2016)
First fossil mammals from the Upper Cretaceous Eagle Formation (Santonian, northern Montana, USA), and mammal diversity during the Aquilan North American Land Mammal Age.
Palaeontologia Polonica 67: 101–126.
Mammalian faunas in North America experienced dramatic change during the Cretaceous, with earlier faunas characterized by eutriconodontans, symmetrodontans, and unspecialized therians giving way to a major diversification of therian lineages by the Campanian– Maastrichtian. The Aquilan North American Land Mammal Age (NALMA), originally based on the well-studied fauna of the Milk River Formation (Santonian) of southern Alberta, records the start of this transition. Notable are first appearances of pediomyoid marsupialiforms and the eutherian Paranyctoides, and last occurrences of eutriconodontans and symmetrodontans. The Campanian Wahweap Formation has yielded a similar fauna, but until now the John Henry Member of the Straight Cliffs Formation was the only other unit of known Santonian age from which fossil mammals have been recovered, leaving this transitional interval represented by limited sampling. The Eagle Formation in central and northern Montana is considered to be laterally equivalent to the Milk River Formation, with northernmost exposures correlated to the upper Santonian, based on palynomorphs and magnetostratigraphy. Here, we describe the first fossil mammals known from the Eagle Formation. A relatively small rock sample yielded a rich, diverse assemblage including two genera of spalacotheriid symmetrodonts, several “alphadontid” marsupialiforms and the large pediomyoid Aquiladelphis, and at least two eutherians including Paranyctoides. Multituberculates, to be described separately, are also abundant and diverse. The Eagle Formation assemblage is broadly similar in composition to that from the Milk River Formation, but shares the spalacotheriid Spalacotheridium with older units, including the Straight Cliffs Formation from southern Utah. These initial results provide another biostratigraphic data point linking Santonian faunas across a broad latitudinal range, and encourage reevaluation of the Aquilan NALMA.
Fostowicz-Frelik, Ł. (2016)
A new zalambdalestid (Eutheria) from the Late Cretaceous of Mongolia and its implications for the origin of Glires.
Palaeontologia Polonica 67: 127–136.
Barunlestes butleri Kielan-Jaworowska, 1975 from the Late Cretaceous of Mongolia was erected as a second genus of Zalambdalestidae, a specialized family of Asiatic Cretaceous eutherian mammals. Since the beginning, the peculiarities of one specimen (MgM-I/135), which could not be attributed to individual variation, led to questioning not only its generic but even family status. Among the differences the most notable are: more enlarged lower incisor (i1), which reaches the end of the tooth row, enamel cover on the i1 only ventral, deeper mandible body, the ultimate lower premolar with more strongly developed trigonid having large metaconid, a well-shaped high paraconid, and the metaconid transversely aligned with the protoconid. Thus, this specimen is herein assigned to Zofialestes longidens gen. et sp. n. It is definitely a zalambdalestid, although the most derived of all genera currently known. On the other hand, a combination of morphological characters shared also with some basal Glires suggests paraphyletic status of Zalambdalestidae and their plausibly ancestral position to the entire Euarchontoglires clade. Key words: Crown placentals, Anagalida
Luo, Z.-X., Meng, Q.-J., Liu, D., Zhang, Y.-G., and Yuan, C.-X. (2016)
Cruro-pedal structure of the paulchoffatiid multituberculate Rugosodon eurasiaticus and evolution of the multituberculate ankle.
Palaeontologia Polonica 67: 149–169.
Here we describe the osteological structures of the lower hind limb and foot of the Late Jurassic Rugosodon eurasiaticus, the earliest-known postcranial fossil of a multituberculate mammal. This fossil extends the key cruro-tarsal apomorphies, previously known from multituberculates of the Cretaceous and Paleogene, to the paulchoffatiid multituberculates of the Jurassic. Multituberculates as a group can now be diagnosed by derived features of the astragalus, the navicular, and the entocuneiform. These features are correlated with the mobility of the upper ankle joint and pedal digit I, indicating that early multituberculates acquired new locomotor functions of the limb and foot. However, the standing pedal posture of the basal multituberculates is plantigrade, typical of primitive mammaliaforms. The digitigrade posture appeared later in derived multituberculates of the Late Cretaceous and Paleogene, and was accompanied by several derived features of the calcaneus: elongation of the calcaneal tuber, development of the peroneal process and groove, and medio-lateral compression of the proximal part of calcaneus. These derived features enhanced locomotor function by increasing the in-lever of the Achilles muscles to lift the calcaneal heel off the substrate. The derived calcaneo-cuboidal features also facilitated a wider range of movement (including abduction) of the distal pedal elements. We concur that derived multituberculates may have had digitigrade pedal posture, although only facultatively. New fossils of the Jurassic Rugosodon and Early Cretaceous Sinobaatar have revealed fresh evidence that the astragalar features of the earliest paulchoffatiids are correlated with sophisticated cruro-tarsal rotation as in other multituberculates. Rugosodon provides the ancestral condition from which more diverse calcaneal features for more versatilefunctions evolved in geologically younger and more derived multituberculates.
Key words: Hind limb, tarsals, multituberculates, mammal
Martin, T., Schultz, J.A., Schwermann, A.H., and Wings, O. (2016)
First Jurassic mammals of Germany: Multituberculate teeth from Langenberg Quarry (Lower Saxony). Palaeontologia Polonica 67: 171–179.
LSID urn:lsid:zoobank.org:pub: AAB91665-4045- 403F-BA29-B9EE46D87EFD
Two multituberculate molars from the Kimmeridgian of the Langenberg Quarry near Goslar (Lower Saxony, Germany) represent the first Jurassic mammals from Germany. An upper M1 with cusp formula 5L/4B is characterized by strongly ornamented enamel and is assigned to Teutonodon langenbergensis gen. et sp. n. within the plagiaulacid line. A second specimen preserving two large and one small cusp is interpreted as a lingual fragment of an eobaatarid m1. It extends the stratigraphic range of Eobaataridae from the Early Cretaceous to the Late Jurassic (Kimmeridgian) The new findings expand the geographic range of multituberculates to Central Europe. Key words: Eobaatarid
Meng, J. and Hou, S.-L. (2016)
Earliest known mammalian stapes from an Early Cretaceous eutriconodontan mammal and implications for transformation of mammalian middle ear.
Palaeontologia Polonica 67: 181–196.
The earliest known mammalian stapes with unequivocal morphology from an Early Cretaceous eutriconodontan, Chaoyangodens lii, is described. The stapes is roughly rectangular in dorsal view with parallel crura and equal width on both the distal and proximal ends. The stapes has a large stapedial foramen and a prominent process that is interpreted as for insertion of the stapedius muscle (PISM). The PISM is homologized with the proximal end of the interhyal, instead of the dorsal process of the sauropsid extrastapes; the latter is fused to the crista parotica of the otic capsule as the tympanohyal in mammals. The morphology of the stapes is probably characteristic of the transitional mammalian middle ear and supports the notion that the rod-like, perforated stapes with a broad end-on contact with the incus is a primitive stapes condition for mammals. During the evolution of mammalian middle ear, the distal end of the stapes and the PISM reduced the size, along with reduction of other ear ossicles. Because the stapedius muscle is absent in monotremes, the columelliform-imperforate stapes of monotremes probably lacks the homologue of the PISM. Key words: Stapes, eutriconodontan, mammal, Cretaceous, middle ear, evolution.
Rougier, G.W., Sheth, A.S., Spurlin, B.K., Bolortsetseg, M., and Novacek M.J. (2016)
Cranio dental anatomy of a new Late Cretaceous multituberculate mammal from Udan Sayr, Mongolia.
Palaeontologia Polonica 67: 197–248.
The multituberculate Mangasbaatar udanii gen. et sp. n., represented by two specimens from Udan Sayr locality in the Gobi desert (Mongolia), is a derived member of a speciose group of Late Cretaceous Mongolian multituberculates (LCMM), clustering together with large-size forms such as Catopsbaatar, Tombaatar, and Djadochtatherium, forming a monophyletic group. Tombaatar sabuli is the sister taxon and shares with the new form the dental formula, overall dental morphology, and approximate size. The new multituberculate has a very large middle ear cavity, housing a petrosal and promontorium that are deeply sunk into the braincase. The expansion of the middle ear cavity seems to be absent among basal LCMM, only developing among members of Djadochtatherioidea, and to an extreme degree in the Udan Sayr multituberculate and Tombaatar. Among living mammals, enlarged middle ear cavities confer enhanced low frequency audition and are often found in fossorial species, such as golden moles, and several groups of rodents adapted to open, arid environments. Burrowing is a possible behavior for the new mammal and its closest relatives with similarly expanded middle ear regions and an arid environment has been proposed for the sediments where most LCMM are found. The new taxon further demonstrates the morphological, and possibly ecological, diversity among multituberculates. Key words: Multituberculata, Djadochtatherioidea, skull structure, phylogeny.
Wang, Y.-Q. and Li, C.-K. (2016)
Reconsideration of the systematic position of the Middle Jurassic mammaliaforms Itatodon and Paritatodon.
Palaeontologia Polonica 67: 249–256.
Two Middle Jurassic mammaliaforms, Itatodon Lopatin et Averianov, 2005 and Paritatodon Martin et Averianov, 2010 have been considered to be members of the Docodonta. Detailed comparison of their dental morphologies with that of typical docodonts shows clearly the differences in cusp pattern and cusp-crest relationship of their lower molar crowns. In docodonts, four crests, originating from the apex of cusp a, extend respectively toward cusps b, g, c, and d, and meet the crests therefrom; all the major crests point to the center of cusps. In contrast, in Itatodon and Paritatodon, only two crests from cusp a extend to cusps g and c, and all the crests reconcile to the anterior or posterior cusp surface. Such differences suggest that the docodont molars function mainly by cutting and crushing, whereas those of Itatodon and Paritatodon have a clear shearing function. Both the morphological features and possible molar occlusal function of Itatodon and Paritatodon distinguish them from the typical docodonts and indicate their shuotheriid affinities. Moreover, the term “pseudotalonid” is used in describing the non-homologous dental features, representing different occlusal relationships, in Shuotheridia and Docodonta. It should thus better be restricted in the description of lower dentition of Shuotheridia, as proposed by the original study. Key words: Itatodon, Paritatodon, Middle Jurassic, pseudotalonid, Docodonta, Shuotheridia. Yuan-Qing Wang [firstname.lastname@example.org
] and Chuan-Kui
Wible, J.R. and Burrows, A.M. (2016)
Does the Jurassic Agilodocodon (Mammaliaformes, Docodonta) have any exudativorous dental features?
Palaeontologia Polonica 67: 289–299.
Obligate exudativory, including active wounding of bark to acquire gum and/or sap, is rare among extant mammals and does not show a consistent dental signature. A recently described Middle Jurassic docodont Agilodocodon was reconstructed as an exudativore based on proposed similarities of its lower anterior dentition to some extant New World monkeys, specifically marmosets, spider monkeys, and howler monkeys. Oddly enough, of these, only marmosets are exudate-feeders. In our reinvestigation, we did not find any significant resemblance in the lower (and upper) anterior dentition between the Middle Jurassic fossil and these extant New World monkeys. The marmosets, the only obligate platyrrhine exudativores, have lower and upper incisors that are distinguished from Agilodocodon and other New World monkeys by having enamel restricted to the labial surface. Differential wear between the enamel and softer dentine maintains a chisel-like tooth that marmosets use in gouging bark. Additional comparisons of the anterior dentition of Agilodocodon and other extant mammals were conducted. The lower and upper anterior teeth of Agilodocodon were found to be most similar to some elephant shrews and South American marsupials, which have a primarily insectivorous diet. Agilodocodon does not show any dental adaptations found in extant mammals for exudativory.