Sinotamias
| Sinotamias | ||||||||||||
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| middle to late Miocene ( Serravallian , Messinian ) to early Pliocene |
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| approx. 14 to approx. 5 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Sinotamias | ||||||||||||
| Qiu , 1991 | ||||||||||||
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Sinotamias is a genus of the squirrels (Sciuridae) from the middle to late Miocene that was extinct in geological times. It was described in 1991 on the basis of fossil finds of Sinotamias gravis , which were made in Inner Mongolia , People's Republic of China , and in addition to this nominate form currentlyincludesfour other species from China, Ukraine and Greece .
features
The characteristics of the post-cranial skeleton of Sinotamias are unknown and probably correspond largely to those of modern ground squirrels such as the chipmunks ( Tamias ). The animals were comparatively small, which differentiates them from the species of the genus Sciurotamias . The genus was described on the basis of a lower jaw and a few individual teeth, so that all known genus-typical features relate to them. The enamel of the lower incisors is grazed by inclined ribs that run anterolateral to the longitudinal axis of the tooth at an angle of 3 to 7 degrees. The upper premolar P4 has a reduced anteroloph and the metaloph is narrowed or separated from the protocone . The upper molars M1 and M2 have metaconules at the posterior approach of the metaloph. The ectolophid of the lower molars m1 and m2 is arched and tapered backwards. The lower molars enlarge from p4 to m3 and they have no anteroconulid, mesoconid and entoconid. The lower jaw is slender, with a flat articular process and a slightly inclined angular process.
The characteristics in which the representatives of the genus Sinotamias differ from them are important for the differentiation from other genera and thus the establishment . In their small body size they stand out from all genera of the ground squirrels with the exception of Ammospermophilus , Ictidomys , Tamias and Xerospermophilus as well as the fossil genus Plesiosciurus , which are also comparatively small. They differ from all fossil and recent ground squirrels in the inclined ribs on the enamel of the incisor teeth and the described design of the molars M1 and M2 as well as m1 and m2. There are also differences in the sculpting of the teeth, which distinguish them from other species.
Locations and chronological classification
Sinotamias fossil finds come from different regions of Eurasia , so that a Palearctic distribution of the genus is assumed. The type material and other finds come from the Ertemte 2, Harr Obo 2 and Moergen II deposits in Inner Mongolia , China . Sinotamias gromovi fossils were found in the Andreevka deposit in the Mykolaiv region , Ukraine , and Sinotamias atsali is native to Maramena , Macedonia , in northern Greece .
The fossil finds are dated in Asia to the period from the early Middle Miocene ( Serravallian ) to the Lower Pliocene and in Europe to the late Middle Miocene ( Messinian ) to the Lower Pliocene.
Fossil History and Taxonomy
The genus Sinotamias was established in 1991 by the Chinese mammalian palaeontologist Zhuding Qiu as part of an inventory of the fossils of several fossil deposits in Inner Mongolia based on the type species Sinotamias gravis . Only a few individual teeth and a jaw fragment of these animals were available to him. In addition to the genus and type species, he also described the species Spermophilus orientalis , which was first introduced into a new genus in 2000 as Prospermophilus orientalis and by Maxim V. Sinitsa 2018 due to the very small differences Sinotamias gravis than Sinotamias orientalis also Sinotamias has been assigned.
By 2018, four species were assigned to the genus, all of which were found in East and Central Asia and only through a partially traditional upper jaw and a few isolated molars . Sinitsa revised the taxonomy on the basis of Topachevsky's find material and, above all, on the basis of genus-typical tooth features in order to distinguish it from other genus. According to the current state of knowledge, the genus therefore consists of five species:
- Sinotamias gravis ( Qiu, 1991 )
- Sinotamias gromovi ( Topachevsky, 1971 ), described as Sciurotamias gromovi Topachevsky, 1971
- Sinotamias orientalis ( Qiu, 1991 )
- Sinotamias atsali ( de Bruijn, 1995 ), described as Tamias atsali de Bruijn, 1995
- Sinotamias primitivus ( Qiu, 1996 ), described as Tamias primitivus Qiu, 1996
As early as 1971, the Russian researcher VA Topachevsky described a well-preserved left lower jaw in the Andreevka site, Mykolaiv region , in southern Ukraine , which he assigned to the species Sciurotamias gromovi and thus to the genus Sciurotamias . Due to its small size, he assigned the species to the relationship of Csakvaromys sciurinus Kretzoi, 1951 , which was synonymous with Spermophilinus bredai (Meyer, 1848) in 2012 . A reassessment of the material from Topachevsky's find confirmed that this is not a representative of Sciurotamias due to its small size and that it must instead be assigned to the genus Sinotamias as Sinotamias gromovi . The species described by Hans de Bruijn in 1995 as Tamias atsali and the species described by Qiu in 1996 as Tamias primitivus were also added to Sinotamias due to their tooth characteristics . In addition to these finds, Sinitsa also classified other individual finds in the close relatives of Sinotamias gromovi in 2018 and synonymized Tamias anatoliensis Bosma, de Bruijn and Wessels, 2013 with Sinotamias primitivus .
The species described as Spermophilinus minutus Zhang and Li, 1982 is also occasionally considered a potential species of the genus Sinotamias , but this is unclear due to the poor material available and it is currently considered as 'Sciuridae incertae sedis'. Sinotamias maximus Tyutkova, 2009 , described as Sinotamias species from Kazakhstan , is assigned by Sinitsa 2018 to the Xerini and there to the fossil genus Kherem Minjin, 2004 due to the tooth characteristics.
Phylogenetic systematics
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Phylogenetic systematics of the Marmotini according to Sinitsa 2018
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Sinitsa developed a phylogenetic system of the Marmotini on the basis of the material available to him and thus on the basis of tooth features , in which he classifies the genus Sinotamias together with the likewise fossil genera Miospermophilus and Plesiosciurus as basic genera of the Marmotini. According to his description, the modern Marmotini in Asia and North America developed from this lineage. The recent genera Sciurotamias and Tamias split off before Sinotamias , together with the fossil genera Palaeosciurus , Spermophilinus and Protospermophilus .
designation
The genus Sinotamias was named after the place where it was found in China ("Sino") and after the similarities of the finds with the chipmunks (genus Tamias ).
supporting documents
- ↑ a b c d e f g h i j k l m n Maxim V. Sinitsa : Phylogenetic position of Sinotamias and the early evolution of Marmotini (Rodentia, Sciuridae, Xerinae). Journal of Vertebrate Paleontology e1419251, 2018. doi : 10.1080 / 02724634.2017.1419251
- ↑ a b c Zhuding Qiu: The Neogene mammalian faunas of Ertemte and Harr Obo in Inner Mongolia (Nei Mongol), China. 8. Sciuridae (Rodentia). Senckenbergiana Lethaea 71, 1991; Pp. 223-255.
- ↑ VA Topachevsky: [Remains of Sciurotamias gromovi (Rodentia, Sciuridae) from the Upper Miocene deposits of the Black Sea area in Ukraine]. Vestnik Zoologii 4, 1971; Pp. 46-50. (Russian).
- ^ A b Hans de Bruijn: The vertebrate locality Maramena (Macedonia, Greece) at the Turolian-Ruscinian boundary (Neogene). 8. Sciuridae, Petauristidae and Eomyidae (Rodentia, Mammalia). Munich Geoscientific Treatises A 28, 1995; Pp. 87-102.
- ↑ Zhuding Qiu: Middle Miocene Micromammalian Fauna from Tunggur, Nei Mongol. Science Press, Beijing 1996.
- ↑ Hans de Bruijn, Anneke A. Bosma: Spermophilinus and Csakvaromys, two names for the same genus of ground squirrel (Tamiini, Sciuridae, Rodentia, Mammalia) from the Neogene of Europe. Annals of the Natural History Museum in Vienna A 114, 2012; Pp. 317-320. ( Download )
literature
- Maxim V. Sinitsa: Phylogenetic position of Sinotamias and the early evolution of Marmotini (Rodentia, Sciuridae, Xerinae). Journal of Vertebrate Paleontology e1419251, 2018. doi : 10.1080 / 02724634.2017.1419251 .