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1
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Snout and orbit of Cretaceous Asian multitiuberculates studied by serial sections

100%
Hurum J. H.
Acta Palaeontologica Polonica
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1994
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tom 39
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nr 2
181-221
The orbital wall in Nemegtbaatar gohiensis and Chulsanbaatar vulgaris, from the Late Cretaceous of the Gobi Desert, Mongolia, comprises a small lacrimal anteriorly, large orbital process of the frontal dorsally, orbitosphenoid posteriorly and maxilla ventrally. Nemegtbaatar also posesses an orbital process of the palatine ventrally, not recognized in Chulsanbaatar. Large frontal sinuses of both taxa are interpreted as related to lack of the sagittal crest. Other anatomical characters found in this study, such as orbital process of the frontal, ossified turbinals, ossified ethmoid and vomer, frontal, sphenoidal and maxillary sinuses, and the presence of the orbital process of palatine in Nemegtbaatar suggest a close relationship of multituberculates to monotremes and therian mammals. By the new data obtained from the serial sections the diagnostic character: orbital process of the palatine absent in Multituberculata, is no longer valid. Ossified ethmoid and maxillary turbinals, characteristic for Monotremata, Vincelestes, Marsupialia and Placentalia, are also present in Multituberculata. The precence of a cribiform plate and the precence of an ossified plate of ethmoid in Multituberculata is shared with Monotremata, Vincelestes, Marsupialia and Placentalia.
2
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The braincase of two Late Cretaceous Asian multituberculates studied by serial sections

100%
Hurum J. H.
Acta Palaeontologica Polonica
|
1998
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tom 43
|
nr 1
21-52
The braincase structure of two Late Cretaceous Mongolian djadochtatherian multituberculates Nemegtbaatar gobiensis and Chulsanbaatar vulgaris from the ?late Campanian of Mongolia is presented based on the two serially sectioned skulls and additional specimens. Reconstructions of the floor of the braincase in both taxa are given. The complete intracranial sphenoid region is reconstructed for the first time in multituberculates. Cavum epiptericum is a separate space with the taenia clino-orbitalis (ossified pila antotica) as the medial wall, anterior lamina of the petrosal and possibly the alisphenoid as the lateral wall, and the basisphenoid, petrosal and possibly alisphenoid ventrally. The fovea hypochiasmatica is shallow, tuberculurn sellae is wide and more raised from the skull base than it is in the genus Pseudobolodon. The dorsal opening of the carotid canal is situated in the fossa hypophyseos. The taenia clino-orbitalis differs from the one described in Pseudobolodon and Lambdopsalis in possessing just one foramen (metoptic foramen). Compared to all extant mammals the braincase in Nemegtbaatar and Chulsanbaatar is primitive in that both the pila antotica and pila metoptica are retained. In both genera the anterior lamina of the petrosal is large with a long anterodorsal process while the alisphenoid is small. A review is given of the cranial anatomy in Nemegtbaatar and Chulsanbaatar.
3
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Postcranial skeleton of a Cretaceous multituberculate mammal Catopsbaatar

63%
Hurum J. H., Kielan-Jaworowska Z.
Acta Palaeontologica Polonica
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2008
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tom 53
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nr 4
We describe an incomplete postcranial skeleton of Catopsbaatar catopsaloides from the ?late Campanian red beds of Hermiin Tsav I, in the Gobi Desert, Mongolia. The skeleton is fragmentary and the preservation of bone surface does not permit reconstruction of the musculature. The studied skeleton contains some parts not preserved or incompletely known in other multituberculate genera, such as a long spinous process in a single lumbar vertebra, which together with long transverse processes preserved in Nemegtbaatar, might indicate that at least some multituberculates had jumping ability. The calcaneus of Catopsbaatar is unusual, differing from most other multituberculates (where known) and other mammals by having a short tuber calcanei, with a large proximal anvil−shaped process strongly bent laterally and ventrally, arranged obliquely with respect to the distal margin of the calcaneus, rather than arranged at 90° to it, as in other mammals. This suggests the presence of strong muscles that attached to the tuber calcanei, perhaps further attesting to jumping abilities in Catopsbaatar. We also describe an unfused pelvic girdle and the first extratarsal spur bone (os cornu calcaris) known in multituberculates.
4
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Limb posture in early mammals: Sprawling or parasagittal

63%
Kielan-Jaworowska Z., Hurum J. H.
Acta Palaeontologica Polonica
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2006
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tom 51
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nr 3
The limb posture in early mammals is a matter of controversy. Kielan−Jaworowska and Gambaryan presented arguments for a sprawling posture in multituberculates, based mainly on three characters of the hind limbs (deep pelvis, mediolateral diameter of the tibia larger than the craniocaudal, and position of MtV, which fits the peroneal groove on the calcaneus and is not aligned with the axis of tuber calcanei). Here we present two more arguments for sprawling hind limbs in early mammals. One is the presence of an os calcaris, supporting the probably venomous spur in hind legs of docodontans, multituberculates, eutriconodontans, and “symmetrodontans”, similar to those of extant monotremes. We argue that early mammals (except for boreosphenidans) had sprawling limb posture and venomous spur; acquisition of the parasagittal stance was apparently characteristic only of boreosphenidans, in which the spur has not been found. The second argument is based on taphonomic evidence from lacustrine conditions (e.g., Early Cretaceous Jehol Biota), in which the mammalian skeletons, except for boreosphenidans (Sinodelphys and Eomaia), have been preserved compressed dorso−ventrally, suggesting sprawling stance. In similar conditions of the Eocene Messel Biota the skeletons of boreosphenidan mammals (except for bats and pangolins) are preserved lying on flanks, suggesting parasagittal stance. Sereno argued that forelimbs in multituberculates were parasagittal, based on the stated presence of a ventrally facing glenoid, a mobile shoulder joint, and an elbow joint with enhanced flexion−extension capability. However, these characters are not unequivocally indicative of parasagittalism. We demonstrate that the structure of the distal end of the multituberculate humerus is condylar, with no tendency for developing a trochlea. We reconstruct multituberculates and other early mammals with sprawling stance in resting position as plantigrade.
5
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Djatochtatheria - a new suborder of multituberculate mammals

63%
Kielan-Jaworowska Z., Hurum J. H.
Acta Palaeontologica Polonica
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1997
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tom 42
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nr 2
201-242
Mongolian Late Cretaceous multituberculates (except Buginbaatar) form a monophyletic group for which the suborder Djadochtatheria is proposed. Synapomorphies of Djadochtatheria are: large frontals pointed anteriorly and deeply inserted between the nasals. U-shaped fronto-parietal suture, no frontal-maxilla contact, and edge between palatal and lateral walls of premaxilla. Large, rectangular facial surface of the lacrimal exposed on the dorsal side of the cranial roof is present in all djadochtatherians, but may be a plesiomorphic feature. It is also possible that in djadochtatherians the postglenoid part of the braincase is relatively longer than in other multituberculates. Djadochtatherians have an arcuate p4 (secondarily subtrapezoidal in Catopsbaatar) that does not protrude dorsally over the level of the molars (shared with Eucosmodontidae), I3 placed on the palatal part of the premaxilla (shared with the eucosmodontid Stygimys and the cimolomyid Meniscoessus). The small number of cusps on the upper and lower molars and no more than nine ridges on p4 are possibly plesiomorphies for Djadochtatheria. The djadochtatherian Nessovbaatar multicostatus gen. et sp. n., family incertae sedis from the Barun Goyot Formation is proposed. New specimens of the djadochtatherian genera Kryptobaatar, ?Djadochtatherium, and Kamptobaatar are described and revised diagnoses of these taxa and Sloanbaatar are given. A cladistic analysis of Mongolian Late Cretaceous multituberculates (MLCM), using Pee-Wee and NONA programs and employing 43 dental and cranial characters, 11 MLCM taxa, five selected Late Cretaceous or Paleocene multituberculate genera from other regions, and a hypothetical ancestor based on the structure of Plagiaulacoidea, is performed. The Pee-Wee program yielded two equally fit trees that confirm the monophyly of MLCM excluding Buginbaatar. Kryptobaatar, Djadochtatherium, Catopsbaatar, and Tombaatar form a clade, for which the family Djadochtatheriidae is proposed. Chulsanbaataris the sister taxon of this clade. Bulganbaatar and Nemegtbaatar are the sister group of all other djadochtatherians. Kamptobaatar, Sloanbaatar, and Nessovbaatar form a separate clade in the Pee-Wee tree. The NONAprogram yielded thirty equally parsimonious trees and a strict consensus tree with a poor resolution.
6
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Giant theropod dinosaurs from Asia and North America: skulls of Tarbosaurus bataar and Tyrannosaurus rex compared

63%
Hurum J. H., Sabath K.
Acta Palaeontologica Polonica
|
2003
|
tom 48
|
nr 2
The skull of a newly prepared Tarbosaurus bataar is described bone by bone and compared with a disarticulated skull of Tyrannosaurus rex. Both Tarbosaurus bataar and Tyrannosaurus rex skulls are deep in lateral view. In dorsal view, the skull of T. rex is extremely broad posteriorly but narrows towards the snout; in Ta. bataarthe skull is narrower (especially in its ventral part: the premaxilla, maxilla, jugal, and the quadrate complex), and the expansion of the posterior half of the skull is less abrupt. The slender snout of Ta. bataaris reminiscent of more primitive North American tyrannosaurids. The most obvious difference between T. rex and Ta. bataar is the doming of the nasal in Ta. bataar which is high between the lacrimals and is less attached to the other bones of the skull, than in most tyrannosaurids. This is because of a shift in the handling of the crushing bite in Ta. bataar. We propose a paleogeographically based division of the Tyrannosaurinae into the Asiatic forms (Tarbosaurus and possibly Alioramus) and North American forms (Daspletosaurus and Tyrannosaurus). The division is supported by differences in anatomy of the two groups: in Asiatic forms the nasal is excluded from the major series of bones participating in deflecting the impact in the upper jaw and the dentary−angular interlocking makes a more rigid lower jaw.
7
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Bone microstructure and growth patterns of early mammals

63%
Chinsamy A., Hurum J. H.
Acta Palaeontologica Polonica
|
2006
|
tom 51
|
nr 2
We present results of the first studies of the bone microstructure of early mammals, based on the Early Jurassic Morganucodon, the Late Cretaceous multituberculates, Kryptobaatar and Nemegtbaatar, and the Late Cretaceous eutherians Zalambdalestes and Barunlestes. Our results show that the two eutherian taxa grew relatively slowly with periodic pauses in growth indicated by the presence of rest lines, while the multituberculates and Morganucodon had a faster rate of bone formation that suggests an overall rapid growth rate that slowed down later in ontogeny. Comparisons of the early mammalian bone microstructure with that of non−mammalian cynodonts, extant monotremes, and placentals are also made, and significant differences in the rate of osteogenesis in the various groups are documented. Our findings suggest differences in the growth rate between the multituberculates and the Mesozoic eutherians, and moreover, both groups appear to have slower growth rates as compared to modern monotremes and placentals. Our results further suggest that the determinate growth strategy typical of extant mammals evolved early in the evolution of the non−mammalian therapsids. We speculate that the sustained, uninterrupted bone formation among the multituberculates may have been an adaptive attribute prior to the K−T event, but that the flexible growth strategy of the early eutherians was more advantageous thereafter.
8
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Osteology and phylogeny of Late Jurassic ichthyosaurs from the Slottsmoya Member Lagerstätte (Spitsbergen, Svalbard)

51%
Delsett L. L., Robert A. J., Druckenmiller P. S., Hurum J. H.
Acta Palaeontologica Polonica
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2019
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tom 64
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nr 4
Phylogenetic relationships within the important ichthyosaur family Ophthalmosauridae are not well established, and more specimens and characters, especially from the postcranial skeleton, are needed. Three ophthalmosaurid specimens from the Tithonian (Late Jurassic) of the Slottsmøya Member Lagerstätte on Spitsbergen, Svalbard, are described. Two of the specimens are new and are referred to Keilhauia sp. and Ophthalmosauridae indet. respectively, whereas the third specimen consists of previously undescribed basicranial elements from the holotype of Cryopterygius kristiansenae. The species was recently synonymized with the Russian Undorosaurus gorodischensis, but despite many similarities, we conclude that there are too many differences, for example in the shape of the stapedial head and the proximal head of the humerus; and too little overlap between specimens, to warrant synonymy on species level. A phylogenetic analysis of Ophthalmosauridae is conducted, including all Slottsmøya Member specimens and new characters. The two proposed ophthalmosaurid clades, Ophthalmosaurinae and Platypterygiinae, are retrieved under some circumstances, but with little support. The synonymy of three taxa from the Slottsmøya Member Lagerstätte with Arthropterygius is not supported by the present evidence.
9
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The middle ear in multituberculate mammals

51%
Hurum J. H., Presley R., Kielan-Jaworowska Z.
Acta Palaeontologica Polonica
|
1996
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tom 41
|
nr 3
253-275
The ear ossicles, preserved in skulls of a tiny Late Cretaceous multituberculate Chulsanbaatar vulgaris from Mongolia are arranged as in modern mammals. This makes the idea of an independent origin of the multituberculates from other mammals unlikely. We report the finding of ear ossicles in Mesozoic multituberculates. Three almost complete incudes and two fragments of malleus are described and compared with those reported in the Paleocene Lambdopsalis and in non-multituberculate mammals. In these Late Cretaceous multituberculates lateral expansion of the braincase is associated with the presence of sinuses and development of extensive masticatory musculature, but not by the expansion of the vestibule, which is moderately developed. It is argued that because of the lateral expansion of the multituberculate braincase, the promontorium is arranged slightly more obliquely with respect to the sagittal plane than in other mammals and the fenestra vestibuli faces anterolaterally, rather than laterally. This results in a corresponding alteration in orientation of the stapes. The epitympanic recess is situated more anteriorly with respect to the fenestra vestibuli than in other mammals. The recess is deep, and the incus must therefore be oriented somewhat vertically. The incus is roughly A-shaped, with crus breve subparallel to the axis of vibration of the malleus. This axis, approximately connecting the anterior process of the malleus and the crus breve of the incus, lies at 45-55º to the sagittal plane in Chulsanbaatar. Probably most multituberculates were similar in this respect. The fragments of the malleus show a very long anterior process, which agrees with the reconstruction of the malleus in Lambdopsalis by Meng & Wyss (1995), and with the partial malleus of Kyptobaatar, described by Rougier et al. (in press)
10
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First three-dimensional skull of the Middle Triassic mixosaurid ichthyosaur Phalarodon fraasi from Svalbard, Norway

51%
Roberts A. J., Engelschion V. S., Hurum J. H.
Acta Palaeontologica Polonica
|
2022
|
tom 67
|
nr 1
11
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New data on anatomy of the Late Cretaceous multituberculate mammal Catopsbaatar

51%
Kielan-Jaworowska Z., Hurum J. H., Currie P. J., Barsbold R.
Acta Palaeontologica Polonica
|
2002
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tom 47
|
nr 3
The Gobi Desert is famous for providing one of the worlds best preserved Cretaceous terrestrial faunas, including dinosaurs and mammals. Beginning with the Central Asiatic Expeditions in the 1920s, through the Polish−Mongolian Expeditions in the 1960s–1970s, Soviet−Mongolian Expeditions in 1970s, and finally the Mongolian Academy−American Museum Expeditions in the 1990s–2000s, the number of complete skulls (see Kielan−Jaworowska et al. 2000 for review) of Cretaceous mammals often associated with postcranial skeletons, found in Mongolia increased to several hundred. In addition to these professional expeditions, there have been other types of trips to Mongolia, also aimed at collecting fossils. The Nomadic Expeditions Company in USA organizes one of these, and has made trips to Mongolia since 1996. During the 1999 Nomadic Expedition, a skull associated with parts of the postcranial skeleton of the multituberculate mammal Catopsbaatar catopsaloides was found. The specimen is more complete than others previously known of this species and brings new data on multituberculate anatomy and ontogenetic variation. In this note we discuss the new data on the structure of C. catopsaloides; the details of its anatomy will be described in subsequent papers by the two first authors.
12
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Skull structure and evolution in tyrannosaurid dinosaurs

51%
Currie P. J., Hurum J. H., Sabath K.
Acta Palaeontologica Polonica
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2003
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tom 48
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nr 2
Tyrannosauridae can be subdivided into two distinct subfamilies—the Albertosaurinae and the Tyrannosaurinae. Previously recognized subdivisions Aublysodontinae and Shanshanosaurinae are rejected because they are based on insufficient material and juvenile specimens. Our results are based upon a phylogenetic analysis using PAUP program (Swofford 1999) of 77 skull characters and seven genera (Albertosaurus, Alioramus, Daspletosaurus, Gorgosaurus, Nanotyrannus, Tarbosaurus, and Tyrannosaurus); with Allosaurus as outgroup. Of the 77 characters used, more than half were parsimony informative. Asingle most parsimonious tree was obtained with the Tree Length being 88. The analysis of cranial characters and comparison of postcranial features reveal that Tarbosaurus bataar is not the sister taxon of Tyrannosaurus rex (contra Holtz 2001). Their similarities are partially due to the fact that both are extremely large animals. Thus, Tarbosaurus should be considered a genus distinct from Tyrannosaurus.
13
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An extended range of the multituberculate Kryptobaatar and distribution of mammals in the Upper Cretaceous of the Gobi Desert

51%
Kielan-Jaworowska Z., Hurum J. H., Badamgarav D.
Acta Palaeontologica Polonica
|
2003
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tom 48
|
nr 2
The Late Cretaceous multituberculate mammal Kryptobaatar dashzevegi Kielan−Jaworowska, 1970 is the most common mammalian taxon in the Upper Cretaceous (?lower Campanian) rocks of the Djadokhta Formation at Bayan Zag¹ (= Bayn Dzak) and Tögrög (= Toogreek), and in the beds of Ukhaa Tolgod in the Gobi Desert. Kryptobaataris also common in the Bayan Mandahu Formation (equivalent of the Djadokhta Formation), Inner Mongolia, China, represented there by K. mandahuensis. Kryptobaatar has not been reported as yet from the younger (?upper Campanian) Baruungoyot Formation nor from its stratigraphic equivalents, the red beds of Hermiin Tsav (= Khermeen Tsav). In this paper we report the discovery of an incomplete skull of Kryptobaatar dashzevegi at Hermiin Tsav I. It is the second mammal species common to the Djadokhta and Baruungoyot Formations (the first being Deltatheridium pretrituberculare). We provide a corrected list of mammals found in the Late Cretaceous localities of the Gobi Desert, and we argue (albeit inconclusively), that mammal evidence shows that the Ukhaa Tolgod beds might be closer in time of deposition to the Djadokhta Formation than to that of the Baruungoyot Formation.
14
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Skull structure in Catopsbaatar and the zygomatic ridges in multituberculate mammals

51%
Kielan-Jaworowska Z., Hurum J. H., Lopatin A. V.
Acta Palaeontologica Polonica
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2005
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tom 50
|
nr 3
The late Campanian djadochtatherioid multituberculate Catopsbaatar catopsaloides was originally known from three skulls from Hermiin Tsav in the Gobi Desert (Mongolia). Three more skulls from Hermiin Tsav are now available, associated with parts of the previously unknown postcranial skeleton, which will be described separately. We describe herein the skull and dentition of C. catopsaloides, based on all available material, housed in PIN, PM, and ZPAL collections. The genera Catopsbaatar, Djadochtatherium, and Kryptobaatar share several characters, unknown in Tombaatar, such as very long postorbital processes directed postero−laterally and downwards, parietal ridges extending from the posterior margins of the postorbital processes postero−medially, and nuchal crests with prominent lateral wings, incurved anteriorly in the middle, so that the skull in dorsal view is shorter in the middle than laterally. Catopsbaatar shares with Djadochtatherium a very high and prominent anterior zygomatic ridge, and presence of the masseteric protuberance, but differs from it and from other djadochtatherioid genera in having the orbit situated more posteriorly, the intermediate zygomatic ridge adhering to the anterior ridge, and a smaller trapezoidal (rather than crescent−shaped) p4 without ridges; it differs from Kryptobaatar and Djadochtatherium in having three upper premolars (P2 being lost) and shares this last character with Tombaatar. Catopsbaataris known not only from Hermiin Tsav, but also from Baruungoyot Formation of Khulsan, represented there by a single m2. We demonstrate that the separation of the masseter superficialis into two parts, the origins of which leave scars on the lateral wall of the zygomatic arch surrounded by zygomatic ridges, occurs in all the multituberculates (beginning with Paulchoffatiidae), and is regarded as a multituberculate autapomorphy.
15
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Were mammals originally venomous?

51%
Hurum J. H., Luo Z. X., Kielan-Jaworowska Z.
Acta Palaeontologica Polonica
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2006
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tom 51
|
nr 1
The extratarsal spur in extant monotremes consists of an os calcaris and a cornu calcaris. A poisonous extratarsal spur occurs only in the platypus (Ornithorhynchus); a possibly secondarily non−poisonous spur is present in echidnas (Tachyglossus and Zaglossus). Some therian mammals (e.g., bats), reptiles (Chamaeleo), and amphibians have a spur−like structure in the ankle, but this is not homologous to the extratarsal spur of monotremes. Among fossil mammals, the co−ossified os calcaris and ossified cornu calcaris have been found in the eutriconodontan Gobiconodon and in the spalacotheroid “symmetrodontan” Zhangheotherium. Here we describe the os calcaris in several multituberculate mammals from the Late Cretaceous of the Gobi Desert, Mongolia. The multituberculate os calcaris is a large, flat bone, generally similar to that in males of the extant monotreme species, but the cornu calcaris is not ossified. In Gobiconodon and Zhangheotherium the ossified cornu calcaris is fused to the os calcaris probably to provide the bony support for the keratinous spur. We hypothesize that the os calcaris in these Mesozoic mammal groups is homologous to that of monotremes. However, the extratarsal spur has not been found in non−mammalian cynodonts nor in other synapsids. A platypus−like os calcaris might be an apomorphic characteristic of basal Mesozoic mammals and is secondarily lost in crown therians; the os calcaris is confirmed to be absent in well−preserved tarsal structures of the earliest known crown therian mammals. We speculate that the os calcaris, the cornu calcaris, and its associated venom gland might have served the function of a defensive structure during the “dark ages” of mammalian history, when dinosaurs ruled the Earth. This structure is a plesiomorphic character retained in extant monotremes and cannot be used as an autapomorphy of Monotremata.
16
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An ankylosaurid dinosaur from Mongolia with in situ armour and keratinous scale impressions

45%
Arbour V. M., Lech-Hernes N. L., Guldberg T. E., Hurum J. H., Currie P. J.
Acta Palaeontologica Polonica
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2013
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tom 58
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nr 1
A Mongolian ankylosaurid specimen identified as Tarchia gigantea is an articulated skeleton including dorsal ribs, the sacrum, a nearly complete caudal series, and in situ osteoderms. The tail is the longest complete tail of any known ankylosaurid. Remarkably, the specimen is also the first Mongolian ankylosaurid that preserves impressions of the keratinous scales overlying the bony osteoderms. This specimen provides new information on the shape, texture, and ar− rangement of osteoderms. Large flat, keeled osteoderms are found over the pelvis, and osteoderms along the tail include large keeled osteoderms, elongate osteoderms lacking distinct apices, and medium−sized, oval osteoderms. The specimen differs in some respects from other Tarchia gigantea specimens, including the morphology of the neural spines of the tail club handle and several of the largest osteoderms.
17
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Large Onychites (Cephalopod Hooks) from the Upper Jurassic of the Boreal Realm

39%
Hammer O., Hryniewicz K., Hurum J. H., Hoyberget M., Knutsen E. M., Nakrem H. A.
Acta Palaeontologica Polonica
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2013
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tom 58
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nr 4
We report on the discovery of large cephalopod arm hooks (mega−onychites) from the Kimmeridgian and Volgian of Spitsbergen (Agardhfjellet Formation). This includes a largely uncompressed hook in a seep carbonate, with preservation of surface sculpture. We suggest the use of logarithmic spirals as morphological descriptors for the outer part of cephalopod arm hooks, with implications for systematics and functional morphology. Comparison with Upper Jurassic material from Greenland, northern Norway and the North Sea demonstrates a remarkably consistent morphology, which we assign to the same form species, Onychites quenstedti. Considering the relatively small stratigraphic (Kimmeridgian–Volgian) and biogeographic (Boreal) range of this large form, it is likely that it represents a single biological species or genus.
18
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First Jurassic mammals from Kyrgyzstan

39%
Nessov L. A., Kielan-Jaworowska Z., Hurum J. H., Averianov A. O., Fedorov P. V., Potapov D. O., Froyland M.
Acta Palaeontologica Polonica
|
1994
|
tom 39
|
nr 3
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