| 1. |
- Sulej, Tomasz, et al.
(författare)
-
The earliest-known mammaliaform fossil from Greenland sheds light on origin of mammals
- 2020
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:43, s. 26861-26867
-
Tidskriftsartikel (refereegranskat)abstract
- Synapsids are unique in having developed multirooted teeth and complex occlusions. These innovations evolved in at least two lineages of mammaliamorphs (Tritylodontidae and Mammaliaformes). Triassic fossils demonstrate that close to the origins of mammals, mammaliaform precursors were "experimenting" with tooth structure and function, resulting in novel patterns of occlusion. One of the most surprising examples of such adaptations is present in the haramiyidan Glade, which differed from contemporary mammaliaforms in having two rows of cusps on molariform crowns adapted to omnivorous/herbivorous feeding. However, the origin of the multicusped tooth pattern present in haramiyidans has remained enigmatic. Here we describe the earliest-known mandibular fossil of a mammaliaform with double molariform roots and a crown with two rows of cusps from the Late Triassic of Greenland. The crown morphology is intermediate between that of morganucodontans and haramiyidans and suggests the derivation of the multicusped molariforms of haramiyidans from the triconodont molar pattern seen in morganucodontids. Although it is remarkably well documented in the fossil record, the significance of tooth root division in mammaliaforms remains enigmatic. The results of our biomechanical analyses (finite element analysis [FEA]) indicate that teeth with two roots can better withstand stronger mechanical stresses like those resulting from tooth occlusion, than teeth with a single root.
|
|
| 2. |
- Niedzwiedzki, Grzegorz, 1980-, et al.
(författare)
-
Non-tetrapod trace fossils from the Middle Devonian tetrapod tracksite at Zachelmie Quarry, Holy Cross Mountains, Poland
- 2020
-
Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 553
-
Tidskriftsartikel (refereegranskat)abstract
- The Middle Devonian (Eifelian) dolomites exposed in the Zachelmie Quarry (Holy Cross Mountains, southern Poland) contain the earliest fossil record of tetrapods. Low-diversity, but unique assemblages of trace fossils characterize the track-bearing interval within the Lower Complex of the Wojciechowice Formation. The reconstructed environment of the trace fossil-rich beds includes ephemeral lakes and/or shallow-water lagoons separated from an open marine area by sparsely vegetated islands and spits. The most abundant non-tetrapod trace fossils from these beds are large, horizontal-to-vertical burrows, and dish-, circular- to oval-shaped, shallow depressions. The burrows are abundant on the upper surfaces of thick dolomicritic beds, especially in some palaeosol levels, but they are also associated with tetrapod trackways. Large, semi-aquatic or terrestrial animals (e.g., arthropods or vertebrates) most likely produced these burrows. The circular- to oval-shaped depressions observed on a large surface and other smaller, isolated blocks from the same stratigraphical level are interpreted as fish feeding/nesting/resting traces. Piscichnus sanctacrucensis isp. nov. is proposed as a new ichnospecies of the oval-shaped fish trace fossil from the Middle Devonian of Poland. A single, medium-sized Undichnia specimen, a fish swimming trace, is associated with the Piscichnus traces. The described trace fossils provide new insight into the palaeoecology and taphonomy of the Middle Devonian tetrapod tracksite from Poland and clarify remaining controversies regarding the interpretation of some poorly preserved trace fossils from the Zachelmie Quarry.
|
|
| 3. |
- Pawlak, Wojciech, et al.
(författare)
-
Dipnoan from the Upper Triassic of East Greenland and remarks about palaeobiogeography of Ptychoceratodus
- 2020
-
Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920 .- 1732-2421. ; 65:3, s. 561-574
-
Tidskriftsartikel (refereegranskat)abstract
- Here we present a description of the dipnoan remains collected from the middle to upper Norian (Upper Triassic) of Jameson Land, East Greenland. The specimens consist of isolated tooth plates and skull bones of Ptychoceratodus, the most complete Late Triassic dipnoan material from Greenland. This genus is reported for the first time from the Upper Triassic of Greenland. The studied material belongs to Ptychoceratodus rectangulus previously known from the middle-upper Norian of Germany. It fills the biogeographical gap between the records of the Germanic and the Jameson Land basins. A reconstruction of the skull roof is provided, based on isolated bones collected from the same bone-bed. Their good preservation enables recognition of the sensory line pits, arranged similarly as in the extant Protopterus, suggesting a comparable mode of life. This finding has implications for our understanding of the disparity in Ptychoceratodus dipnoans, as well as the morphology between closely related dipnoans of the Late Triassic ecosystems.
|
|
| 4. |
- Pindakiewicz, Maciej, et al.
(författare)
-
Feeding convergence among ray-finned fishes : Teeth of the herbivorous actinopterygians from the latest Permian of East European Platform, Russia
- 2020
-
Ingår i: Acta Palaeontologica Polonica. - : INST PALEOBIOLOGII PAN. - 0567-7920 .- 1732-2421. ; 65:1, s. 71-79
-
Tidskriftsartikel (refereegranskat)abstract
- A unique functional adaptation to herbivory within early ray-finned fishes is exemplified by the late Permian actinopterygians within the family Etuynotoidiidae with policuspid teeth strongly modified with respect to the primitive actinopterygian conditions. Here we report additional finds of multidenticulated teeth from the fluvial latest Permian deposits of Russia. The teeth belong to the members of endemic Eurynotoidiidae and show rather high morphological diversity. We confirm that the Russian forms are the earliest known ray-finned fishes with substantial modifications of teeth adapted to the processing of food. These finds confirm some previous suggestions that the adaptation to herbivory first developed in freshwater fishes, not marine. We found very similar dental adaptations in some groups of Recent freshwater teleosts, especially in characifonns and cichlids. It suggests that sympatric species of Permian Eurynotoidiidae explored various herbivorous niches like modem fish in East African lakes. Apparently, this first pulse of adaptive radiation in ray-finned fishes was probably caused by diversification of Permian aquatic vertebrate community.
|
|
| 5. |
- Sulej, Tomasz, et al.
(författare)
-
A new early Late Triassic non-mammaliaform eucynodont from Poland
- 2020
-
Ingår i: Historical Biology. - : TAYLOR & FRANCIS LTD. - 0891-2963 .- 1029-2381. ; 32:1, s. 80-92
-
Tidskriftsartikel (refereegranskat)abstract
- Bicuspid, tricuspid and tetracuspid postcanine teeth of a new non-mammaliaform eucynodont, Polonodon woznikiensis gen. et sp. nov. from the mid-late Carnian (early Late Triassic) of Wozniki clay-pit, Silesia (southern Poland) show incipient root division. They are similar to teeth of Dromatheriidae from the Carnian (early Late Triassic) to the Rhaetian (late Late Triassic) of Europe, India, and USA and the dentition of brasilodontids from the early Norian (mid Late Triassic) of Brazil. The P. woznikiensis teeth differ from those of the latter group mostly in the absence of cingulum. Some of the new fossils from Silesia provide the oldest Laurasian record of eucynodont teeth with the main cusp (a) anterior edge very long as the mesial cusp b is placed much lower than cusp c (distal). The contemporaneous Alemoatherium huebneri, from Gondwana, had similar postcanines. The findings from Poland indicate that this postcanine morphology was present in non-mammaliaform cynodonts from both hemispheres as early as the mid-late Carnian. The distal end of the humerus from the same locality is also described.
|
|
