Palaeosinopa

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Palaeosinopa
Skeleton of paleosinopa

Skeleton of paleosinopa

Temporal occurrence
Middle Paleocene to Lower Eocene
59.2 to 47.8 million years
Locations
Systematics
Synapsids (Synapsida)
Mammals (mammalia)
Higher mammals (Eutheria)
Pantolesta
Pantolestidae
Palaeosinopa
Scientific name
Palaeosinopa
Matthew , 1901

Palaeosinopa is a now extinct genus of mammals from the Pantolestidae family. The animals resembled today's insectivores and lived from the Upper Paleocene to the Lower Eocene between 59 and 48 million years ago. Evidence is known mainly from North America , less often from Europe . Significant finds, including some complete skeletons, come from the Northwest of the USA , the Fossil Butte Member of the Green River Formation with an age of around 52 million years and the stratigraphically somewhat older Willwood Formation are particularly outstanding. The representatives of Palaeosinopa were characterized by a robust build and a long tail. The shorter front legs compared to the longer rear legs appeared rather primeval. Due to the body structure, a semi-aquatic way of life is reconstructedfor the animals, the structure of the teeth in turn speaks for predominantly animal food. As a result, Palaeosinopa seemsto have inhabited a habitat similar to that of today's otters . The research history of the genus goes back to the beginning of the 20th century, fossil finds were known earlier, but assigned to other mammal forms.

description

Palaeosinopa was a medium-sized representative of insectivore-like mammals. Large animals achieved a head-torso length of 57 cm using a few complete skeletons from the Fossil Butte Member of the Green River Formation . In addition, there was a tail up to 51 cm long, which thus reached the length of the trunk and thus represented a characteristic feature. The assumed body weight was around 5 kg. Palaeosinopa was compact in build with short limbs, with the hind legs longer than the front ones. This is a rather primitive feature for higher mammals , as is the upward curve of the back. As a result, Palaeosinopa resembled its European relative Buxolestes , but was not quite as robust as this and sometimes larger.

Skull and mandible of Palaeosinopa

The skull measured approximately three to four inches in length and was relatively flat. It had an only moderately elongated rostrum , the greatest width of which was just behind the last molar . The nasal bone was built narrow and pulled far back so that it ended shortly before the orbit . There was a large nasal cavity between the nasal bone and the median jawbone . There was a small constriction behind the eyes (postorbital constriction), which is typical for later representatives of the Pantolestidae. The occiput showed clear stretching to the rear and had a broad shape when viewed from the rear. It also had a strong neck bulge as a muscle attachment surface. On the top of the skull, the two parietal bones formed a small and rather weakly shaped crest .

The lower jaw was sturdy and measured about 5.9 to 7.6 cm, with the bone body reaching up to 1 cm in height below the first molar. The symphysis was long and extended to the second premolar . The bit was the complete tooth number of early mammals and higher had the following dental formula: . The incisors of the lower jaw reached roughly all the same dimensions, in the upper jaw the third incisor was enlarged and conically pointed ( caniniform ). The canine became significantly larger, with a raised rib on the tongue side on the upper one. There was a short diastema to both the incisors and the posterior dentition . The premolars had a simple structure with pointed enamel cusps on the chewing surfaces. There were two on the first two premolars, and their number increased on the back. The size of the anterior molars also increased towards the rear, and some representatives of Palaeosinopa did not show a closed row of premolars. The molars had a typical tribosphenic structure. On the chewing surfaces of the mandibular molars, the highest tooth cusps were arranged in a characteristic group of three ( trigon ) with a deep groove behind it, followed by two further, but significantly smaller cusps ( talon ). In addition, the teeth here showed greater lengths than widths. In the upper jaw there were two, sometimes rounded, tooth cusps on the outer edge (paraconus and metaconus), the third cusp (protoconus) was indented further inwards and was very high and pointed. Overall, the molars in the upper jaw were characteristic of the tribosphenic structure, wider than long. With regard to the pattern of the occlusal surface, Palaeosonopa showed a strong variation, as some forms in the course of their tribal history show a tendency from sectorial (pointed) cusps to bunodont (rounded) ones. The size of the upper molars in large animals was approximately 5 mm in length and 7 mm in width.

The body skeleton of Palaeosinopa is known from several skeletal finds. The spine consisted of 7 cervical, 13 thoracic, 6 lumbar, 3 sacrum and 30 caudal vertebrae, the number of caudal vertebrae is slightly larger than in Buxolestes . The axis in particular , the second cervical vertebra, was characterized by an extremely long spinous process. The anterior vertebrae of the caudal spine, especially marked on the 7th vertebra, also had wing-like broad transverse processes. The humerus had strong muscle attachment points and was rather short and strong with a length of 5.8 cm. At 6.6 cm, the ulna was slightly longer , which was also characterized by a massive upper joint ( olecranon ) that took up about a third of the total length of the bone. As with Buxolestes , the ulna was not fused with the spoke . The femur and shin were about the same length, 7.3 and 7.2 cm, respectively. There was a massive joint head on the femur and a clearly pronounced third trochanter on the shaft. The tibia and fibula were not fused at the ends and were clearly far apart. The front and rear feet ended in five-pointed hands and feet that were rather primeval. The central ray (III) of the front and rear feet each had the greatest length. The foot clearly exceeded the hand in length and size. The third metacarpus was about 2 cm long and the third metatarsus 2.9 cm long. Furthermore, the toes of the front feet were clearly narrowed on the sides and not as wide as those of the hind feet.

Fossil finds

Lower jaw of Palaeosinopa

Palaeosinopa has been recorded in North America from the Upper Paleocene and Lower Eocene between 59 and 48 million years ago . A large concentration of finds is in the northwest of the USA . Numerous finds were known, especially from the state of Wyoming . The Fossil Butte Member of the Green River Formation in southern Wyoming is important. Here, three almost complete skeletons were discovered in a fossil-rich section, one of which is more disarticulated. One of the skeletons represents a young animal and is significantly smaller than the others with a skull of 6.6 cm in length. The finds are dated to an age of 50 to 52 million years and thus belong to the Lower Eocene ( locally stratigraphically the North American fauna zone of the Upper Wasatchium and assigned to the Lostcabinian ). Other areas of the Green River Formation also contained finds of Palaeosinopa , but these are mostly in the form of tooth remnants. Fossil remains from the Wasatch Formation are similarly fragmented , the deposits of which are partially interlocked with those of the Green River Formation. An incomplete skull is already known from the Upper Paleocene of the Hoback Formation in central-western Wyoming, which appeared in the Dell Creek Quarry in Sublette County . Other significant fossil finds were discovered in the Willwood Formation of the Bighorn Basin . These include several hundred found objects, including various skull and dentition parts as well as numerous postcranial skeletal material as well as a partial skeleton. The latter is the oldest known of the genus so far , with a dating at the base of the Lower Eocene (Lower Wasatchian, or here Sandcouleean and Graybullian ). Only three species are recorded in the Willwood formation. Two smaller ones can be found in the lower area of ​​the rock unit, while a larger one stratigraphically spreads further. The material used to describe the genus also comes from the Bighorn Basin, which includes an upper and lower jaw with heavily chewed teeth. Furthermore, numerous finds, including parts of the body skeleton from the Lower Ocene Wasatch Formation in the Powder River basin, were brought to light.

The Roche Percée local fauna of southeastern Saskatchewan in western Canada has also reported a high number of isolated teeth and several mandibles. They come from a coal mine in which deposits of the Ravenscrag Formation are exposed and were largely recovered under water. However, with more than 50 found objects, the collection is one of the largest in Palaeosinopa from the Upper Palaeocene around 59 million years ago. With Besseocetor and Aatotomus there are two other representatives of the Pantolestids, which are represented by significantly less finds. Apart from this area of ​​discovery of the Rocky Mountains , finds of individual teeth come very far south from the red hot local fauna of the plains of the Gulf coast of the state of Mississippi . The finds date from the transition from the Paleocene to the Eocene. The northernmost finds, however, represent those of the Margaret Formation on Ellesmere Island in the arctic north of Canada, which in turn include individual molars. The age of the fossil-bearing layers of the Margaret Formation ranges from the Lower Eocene to the transition to the Middle Eocene.

In Europe , Palaeosinopa has only come down to us from the Lower Eocene . For example, a mandibular fragment with the attached rear molars from the Paris pelvis was described, while several isolated teeth exist from northern France, including one from Prémontré in the Aisne department in the form of a single molar. Half a dozen teeth still come from the important Dormaal site in Belgium.

Paleobiology

The skeleton of Palaeosinopa is similar to that of its European relative Buxolestes and is generally robust with short legs and strong muscle attachment points. Overall, however, the animals were significantly larger and slimmer than Buxolestes and had a longer tail. As a result, Palaeosinopa also has certain similarities to today's fish ( Lutra ) or New World otters ( Lontra ), which suggests a semi-aquatic way of life. These similarities are indicated, among other things, by the strong spinous processes on the cervical vertebrae and the massively pronounced occiput , which indicate a well-developed neck musculature. Further features of adaptation to swimming are the short and wide humerus , the shaft of which is slightly rotated, or the caudal vertebrae, which have greatly broadened transverse processes in the front half of the tail. These, too, point to strong muscles in this area, whereby the tail made swimming easier by moving up and down or by winding sideways. In addition, there is little evidence of a semi-aquatic way of life on the limbs. The rear legs are significantly longer than the front legs, which is more of a primeval characteristic. In contrast to today's semi-aquatic swimmers, the thighbone and the shinbone are about the same length, the otter has a longer shinbone than the thighbone, which facilitates the leverage when paddling. The rear feet are 50% larger than the front feet. They indicate an important function when swimming, as more water can be displaced when swimming. However, the front and rear feet have very wide phalanges . This characteristic is again typical for burrowing animals such as the armadillos , but these have larger forefeet than the rear as a further adaptation to this way of life. However, since the ulna has a particularly large upper joint, which also occurs in the same way in the armadillos, it can be concluded that there is an at least partially burrowing way of life, which is also indicated by the longer third toe of the front feet. Overall, Palaeosinopa appears as an otter-like or beaver-like animal that lived on the banks of ponds and rivers, looked for food in the water and probably built protective structures in the bank area.

Numerous bone fragments and small bone platelets originate from the gastrointestinal area of ​​one of the complete skeletons from the Fossil Butte Member . These can largely be put to Diplomystus , a species of fish that occurs very frequently there . This indicates that Palaeosinopa ate a predatory diet, which, however, could already be assumed on the basis of the structure of the dentition with the pointed molars. Similar findings on nutrition are known from Buxolestes in Europe. On the other hand, with reference to the only moderately long snout and typical abrasion patterns on the teeth, compared to today's sea ​​otters , some researchers also see a certain specialization in molluscs such as mussels . Due to the structure of the skull with the postorbital constriction and some prominent muscle attachment points, very strong muscles with high biting force are reconstructed.

Systematics

Closer relationship of the Pantolesta according to Hooker 2013
  Leptictida  

 Pseudorhyncocyonidae


   


 Leptictidae


   
  Pantolesta  

 Aphronorus


  Pantolestidae  

 Coriphagus


   

 Bessoecetor


   

 Palaeosinopa


Template: Klade / Maintenance / 3


   

 Palaeanodonta






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William Diller Matthew

Palaeosinopa is a genus of the family of Pantolestidae . The Pantolestidae were primeval insectivore-like animals and occurred from the Middle to Upper Paleocene to the Lower Oligocene in North America and Eurasia , but are also found in the transition from the Paleocene to the Eocene in northern Africa . The internal as well as the external relationships of the Pantolestidae have not yet been adequately clarified. They are often considered to be members of the subordination of the Pantolesta within the order of the Cimolesta , a group of early insectivore-like mammals with, under certain circumstances, closer ties to the Ferae . Other authors refer the Pantolesta in turn to a superordinate group called Proteutheria , which is seen in the close relationship of the insectivores. In general, Pantolesta are considered to be more basal within the higher mammals . A 2013 study sees closer relationships with the Leptictida and the Palaeanodonta . Within the Pantolestidae, Palaeosinopa belongs to the subfamily of the Pantolestinae , whose representatives, in contrast to those of the Pentacodontinae, have clear adaptations to a semi-aquatic way of life. In the closer relationship of palaeosinopa can Pantolestes from the Middle Eocene of North America and Pagonomus from the Middle Paleocene and buxolestes be provided from the Middle Eocene of Europe. Pagonomus , which has been handed down from Walbeck in Saxony-Anhalt , among other places, is partially synonymous with Palaeosinopa , but Pagonomus has recently been listed as an independent genus again. The origin of the Pantolesta is partly seen with the Leptictida. These are already known from the Upper Chalk .

Numerous species have been described in the course of research history, the following are widely recognized:

The systematic position of P. simpsoni is unclear , which was formed by Leigh Van Valen in 1967 from the species P. senior by splitting the finds into Paleotomus senior from the family of Palaeoryctidae and P. simpsoni . However, P. simpsoni was reunited with Paleotomus senior in 1980 by Philip D. Gingerich and the genus was moved to the Pantolestidae. However, P. simpsoni continued to be listed as an independent species thereafter. The best-studied species is P. didelphoides , of which three complete skeletons from the Fossil Butte Member of the Green River Formation are known, including that of a young animal. Young animals have a significantly duller snout than adult animals, the length of the rows of teeth is also noticeably shorter and the diastemas are absent, so that these features were only fully developed in adulthood. This means that there is the possibility that some closely related species, which have only been described on the basis of skull and dentition features, may only represent different growth forms of a species. While all other species are known from North America, P. osborni and P. russelli are the European representatives.

The first finds of Palaeosinopa , including a fragment of a lower jaw, came from the Wind River Basin in North America and were placed in 1881 by Edward Drinker Cope to the genus Ictops , which he incorporated within the predator-like Creodonta . The earliest European finds come from the Paris Basin at the end of the 19th century and were described by Victor Lemoine in 1891 as belonging to Adapisorex , an early mammal that was also insectivorous. It was not until the mid-1960s that it was recognized as belonging to Palaeosinopa . The first description of the genus palaeosinopa was made in 1901 by William Diller Matthew . The holotype (copy number FM 95) comprises an upper and lower jaw with the preserved posterior teeth from the second premolar to the last molar, but the teeth are heavily chewed. The find comes - along with other associated jaw fragments - from the Bighorn Basin and belongs to the Lower Eocene . Matthew had used the name Palaeosinopa informally as early as 1899. In his first description he also referred the genus to the Creodonta, in today's view more precisely to the group of the Hyaenodonta . Matthew also did not establish a relationship with the then already known, closely related representative Pantolestes . However, more exact comparisons of the two genera only enabled new finds from an expedition of the American Museum of Natural History in 1903 to the Bridger Basin in southwestern Wyoming, which brought numerous material from Pantolestes . In 1909, Matthew made a brief mention of Palaeosinopa as one of the Pantolestidae. More extensive descriptions of the genus were made in 1918. The name Palaeosinopa refers to the rather primitive ( παλαιός ( palaiós ) is Greek for "old") design of the molars compared to Sinopa , a genus from the Hyaenodonta group, near which Palaeosinopa originally was was posed by Matthew.

Individual evidence

  1. ↑ a b c d e f g h Kenneth D. Rose and Wighart von Koenigswald: An exceptionally complete skeleton of Palaeosinopa (Mammalia, Cimolesta, Pantolestidae) from the Green River Formation, and other postcranial elements of the Pantolestidae from the Eocene of Wyoming ( UNITED STATES). Palaeontographica A 273, 2005 (3-6), pp. 55-96
  2. ↑ a b c d John A. Dorr: Partial skull of Paleosinopa simpsoni (Mammalia, Insectivora), latest Paleocene Hoback Formation, central western Wyoming, with some general remarks on the family Pantolestidae. Contributions from the Museum of Paleontology, The University of Michigan 24, 1977, pp. 281-307
  3. ^ A b Rachel H. Dunn and Kenneth D. Rose: Evolution of early Eocene Palaeosinopa (Mammalia, Pantolestidae) in the Willwood Formation of the Bighorn Basin, Wyoming. Journal of Paleontology 89 (4), 2015, pp. 665-694
  4. ^ A b William Diller Matthew: Part V: Insectivora (continued), Glires, Edentata. In: William Diller Matthew and Walter Granger (Eds.): A revision of the lower Eocene Wasatch and Wind River faunas. Bulletin of the American Museum of Natural History 34, 1918, pp. 565-657 (pp. 586-592)
  5. ^ Lance Grande: The lost world of Fossil Lake. Snapshot from deep time. University of Chicago Press, Chicago and London, 2013, pp. 1–425 (pp. 263–267)
  6. ↑ a b Kenneth D. Rose, Rachel H. Dunn and Lance Grande: A New Skeleton of Palaeosinopa didelphoides (Mammalia, Pantolesta) from the Early Eocene Fossil Butte Member, Green River Formation (Wyoming), and Skeletal Ontogeny in Pantolestidae. Journal of Vertebrate Paleontology 34 (4), 2014, pp. 932-940
  7. ↑ John-Paul Zonneveld, Gregg F. Gunnell and William S. Bartels: Early Eocene fossil vertebrates from the Southwestern Green River Basin, Lincoln and Uinta Counties, Wyoming. Journal of Vertebrate Paleontology 20 (2), 2000, pp. 369-386
  8. ^ A b Gregg F. Gunnell, John-Paul Zonneveld and William S. Bartels: Stratigraphy, mammalian paleontology, paleoecology, and age correlation of the Wasatch Formation, Fossil Butte National Monument, Wyoming. Journal of Paleontology 90 (5), 2016, pp. 981-1011
  9. ^ A b Thomas M. Bown and David Schankler: A review of the Proteutheria and Insectivora of the Willwood Formation (lower Eocene), Bighorn Basin, Wyoming. United States Geological Survey Bulletin 1523, 1982, pp. 1-79 (pp. 20-30)
  10. ^ A b William Diller Matthew: Additional Observations on the Creodonta. Bulletin of the American Museum of Natural History 14, 1901, pp. 1–38 (pp. 22–23)
  11. ^ A b Brian Daniel Rankin: Early late Paleocene mammals from the Roche Percée local fauna, southeastern Saskatchewan, Canada. University of Alberta, 2009, pp. 1–138 (pp. 53–59)
  12. ^ A b Brian D. Rankin: New pantolestids (Mammalia, Eutheria) from the late Paleocene (late middle Tiffanian) Roche Percée local fauna, southeastern Saskatchewan, Canada. Journal of Paleontology 88 (6), 2014, pp. 1199-1211
  13. ^ A b K. Christopher Beard and Mary R. Dawson: Early Wasatchian Mammals of the Red Hot Local Fauna, Uppermost Tuscahoma Formation, Lauderdale County, Mississippi. Annals of Carnegie Museum 78 (3), 2009, pp. 193–243 (pp. 201–204)
  14. ↑ Jaelyn J. Eberle and Malcolm C. McKenna: Early Eocene Leptictida, Pantolesta, Creodonta, Carnivora, and Mesonychidae (Mammalia) from the Eureka Sound Group, Ellesmere Island, Nunavut. Canadian Journal of Earth Sciences 39, 2002, pp. 899-910
  15. ↑ Jaelyn J. Eberle and David R. Greenwood: Life at the top of the greenhouse Eocene world - A review of the Eocene fl ora and vertebrate fauna from Canada's High Arctic. Geological Society of America Bulletin; January / February 124 (1/2), 2012, pp. 3–23
  16. ^ Richard Smith: Les Pantolestides (Mammalia, Pantolesta) de L'Eocène inférieur de Prémontré (Aisne, France). Palaeovertebrata 30 (1-2), 2001, pp. 11-35
  17. ↑ a b c Thierry Smith: Palaeosinopa ruselli n. Sp. (Mammalia, Pantolesta), taxon du Membre de Dormaal (Belgique), proche de la limite Paléoène-Eocène. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre 67, 1997, pp. 153-160
  18. ↑ a b Kenneth D. Rose: The importance of Messel for interpreting Eocene mammalian faunas Holarctic. Palaeobiology Palaeoenvironment 92, 2012, pp. 631-647
  19. ^ A b c Philip D. Gingerich: A new species of Palaeosinopa (Insectivora, Pantolestidae) from the late Paleocene of western North America. Journal of Mammalogy 61, 1980, pp. 449-454
  20. ↑ a b Jerry J. Hooker: Origin and evolution of the Pseudorhyncocyonidae, a European Paleogene famaly of insectivorous placental mammals. Palaeontology 56 (4), 2013, pp. 807-835
  21. ↑ Malcolm C. McKenna: Toward a phylogenetic classification of the Mammalia. In W. Patrick Luckett and Frederick S. Szalay (Eds.): Phylogeny of the primates: a multidisciplinary approach. New York, London, 1975, pp. 21-46
  22. ↑ Malcolm C. McKenna and Susan K. Bell: Classification of mammals above the species level. Columbia University Press, New York, 1997, pp. 1-631 (pp. 217-219)
  23. ↑ Kenneth D. Rose: The beginning of the age of mammals. Johns Hopkins University Press, Baltimore, 2006, pp. 1–431 (pp. 94–118)
  24. ↑ a b c d Leigh van Valen: New Paleocene insectivores and insectivore classification. Bulletin of the American Museum of Natural History 135, 1967, pp. 217-284 (pp. 222-230)
  25. ^ A b Gregg F. Gunnell, Thomas M. Bown, Jonathan I. Bloch and Douglas M. Boyer: Proteutheria. In: Christine M. Janis, Gregg F. Gunnell and Mark D. Uhlen (eds.): Evolution of Tertiary Mammals of North America: Vol. 2, Small Mammals, Xenarthrans, and Marine Mammals. Cambridge University Press, 2008, pp. 63-81
  26. ↑ Kenneth D. Rose, Gerhard Storch and Katrin Krohmann: Small-mammal postcrania from the middle Paleocene of Walbeck, Germany. Paleontological Journal 2013
  27. ↑ Doug M. Boyer and Justin A. Georgi: Cranial Morphology of a Pantolestid Eutherian Mammal from the Eocene Bridger Formation, Wyoming, USA: Implications for Relationships and Habitat. Journal of Mammalian Evolution 14, 2007, pp. 239-280
  28. ↑ David W. Krause and Philip D. Gingerich: Mammalian fauna from Douglass Quarry, Earliest Tiffanian (Late Paleocene) of the Eastern Crazy Mountain Basin, Montana. Contributions from the Museum of Paleontology The University of Michigan 26 (9), 1983, pp. 157-196
  29. ^ William Diller Matthew: A Provisional Classification of the Fresh-Water Tertiary of the West. Bulletin of the American Museum of Natural History 12, 1899, pp. I9-75 (p. 31)
  30. ^ A b William Diller Matthew: The Carnivora and Insectivora of the Bridger Basin, middle Eocene. Memoirs of the American Museum of Natural History 9, 1909, pp. 291-567 (pp. 522-534)

Web links

Commons : Palaeosinopa  - collection of images, videos and audio files