Aumelasia

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Aumelasia
Aumelasia skeleton

Aumelasia skeleton

Temporal occurrence
Lower to Middle Eocene
50.7 to 43.4 million years
Locations
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Artiodactyla (Artiodactyla)
Dichobunidae
Dichobuninae
Aumelasia
Scientific name
Aumelasia
Sudre , 1980

Aumelasia is a now extinct genus of early artifacts and is generallyassigned tothe family Dichobunidae . It lived in the Lower and Middle Eocene between 51 and 43 million years ago and is known from finds from Western and Central Europe . Three almost complete skeletons from the Messel Pit are significant. These show that Aumelasia was a small representative of the ungulates, which, like other early forms, had an upwardly curved back and short front and long hind legs, as well as an extremely long tail. Indications of leftover food indicate that it mainly fed on seeds and fruits. Thegenus was first described in 1980.

features

Aumelasia was a small representative of the very early artifacts , which in its overall habitus did not reach the dimensions of the close relative Messelobunodon . Typical features of the representatives were a massive head and graceful torso, as well as the short front and long hind legs characteristic of the primitive cloven-hoofed, as well as the upwardly curved spine. In addition, the tail was extremely long and almost reached the length of the trunk with 24 to 25 cm. The skull was 9.2 cm long and had a short anterior skull area. Furthermore, he had only a small nasal space between the median jawbone and the nasal bone . The zygomatic arch was relatively broad and more massive than the related Messelobunodon . At the contact points of the pair of parietal bones there was a strongly developed parietal crest , which in turn is largely absent in Messelobunodon . The eye window was oval in shape with a width of 1.7 cm and a height of 1.2 cm. With a length of 8.5 cm and a bone height of 1.3 cm below the last premolar and first molar, the lower jaw was comparatively massive, which is also evident from the joint attachments, which protrude up to 4.8 cm. The bit included the costs of early higher mammals typical number of teeth, the dental formula was thus: . The small incisors , which mostly had a spatula-shaped shape, were noticeable , but the outer one of the upper jaw differed with its conical, pointed ( canin- shaped ) structure. The lower canine, in turn, resembled the other incisors ( incisiform ). In contrast to messelobunodon , a short, approximately 3 mm long postcanine diastema occurred only rarely , for example between the lower second and third premolars in some representatives. The premolars characterized one or two enamel cusps , the molars four to five. A special feature of the upper molars was an additional central cusp, the mesostyle, located on the lateral edge. Overall, these bumps were designed rather round, which gave the chewing surface a bunodontic appearance. The largest and widest tooth was represented by the second molar, which was up to 6.8 mm long and 8.9 mm wide.

The body skeleton was rather light. The entire spine reached over 52 cm in length, almost half of which was taken up by the tail. This consisted of 24 vertebrae, which are as many as Messelobunodon . The short front and long hind legs are striking. The humerus reached up to 7.9 cm in length, the ulna up to 7.6 cm. The thigh bone was 9.2 cm long and, in contrast to Messelobunodon, had no third trochanter as a muscle attachment point. The shin was almost the same length . Typically for the early cloven-hoofed animals, the hands were made up of five, but the feet were made up of four rays, of which rays III and IV showed the strongest bone formation, analogous to today's articulated ungulates. The metatarsal bones of both rays measured up to 5 cm, the corresponding metacarpal bones were markedly shorter at 2.8 cm.

Fossil record

Aumelasia fossil remains are known from Central and Western Europe and date to the Lower and Middle Eocene between 51 and 43 million years ago. The first known finds come from southern France, from Aumelas , and belong to the late Middle Eocene. They include, among other things, a fragmented upper jaw with the preserved posterior premolar and the three molars, which was used to establish the genus in 1980. Only three years later it was possible to put these finds aside, such as jaw fragments and isolated teeth. They came to light in the Paris Basin and belong to the uppermost section of the Lower Eocene. The most important finds to date were found in the Messel mine near Darmstadt in Hesse. It comprises three, largely complete skeletons, which, as usual, lay on their side for a large part of the Messel mammal finds. Since most of the bone sutures of the long bones were not yet fused and the rear teeth are characterized by the replacement of the deciduous by the permanent teeth, all three individuals can be addressed as young animals. Like the site, they can be traced back to the beginning of the Middle Eocene and are therefore around 47 million years old. From the Geiseltal near Halle in Saxony-Anhalt , several lower and upper jaw parts as well as skull fragments or individual teeth were reported that come from the local lower and partly also from the upper middle coal and are therefore somewhat younger than the skeletons of Messel. They are assigned a total of two types.

Paleobiology

The strikingly graceful physique with the long hind and shorter front legs suggests a similar locomotion as in other early cloven-hoofed animals, such as Messelobunodon . So Aumelasia was probably like this a flight animal that escaped danger with quick leaps. Since the lower leg sections (tibia and fibula) were shorter than Messelobunodon , Aumelasia probably did not have the same speed. Due to the tropical to subtropical forests in Messel and Geiseltal, the representatives of Aumelasia may have lived as shy "bush hats" in the undergrowth.

The bunodonte structure of the posterior set of teeth indicates a herbivorous diet, which probably included leaves and fruits. In two of Messel's three skeletons, food residues could be detected in the gastrointestinal area. In addition to sand , these mainly contained seeds and fruit residues. The composition of the food residues, including the amount of sand, indicates that Aumelasia probably looked for its food mainly on the ground.

Systematics

Aumelasia is a genus of the extinct family of Dichobunidae . The Dichobunidae belong to the most primitive forms from the order of the artifacts . They had a generally very small build and an upwardly curved back and had very long tails, while the front legs were always shorter than the hind legs. Within the Dichobunidae, Aumelasia is placed in the subfamily Dichobuninae with a close relationship to Messelobunodon , which is also passed down from Messel and the Geiseltal. The dichobunidnae are characterized by an only moderately elongated snout, furthermore by a more generalized, bunodontic rear dentition. As a precursor form of Aumelasia is Protodichobune accepted from the Lower Eozän that as Aumelasia had a striking fifth tooth enamel cusps (Mesostyl) on the second upper molar. In contrast to this, the Eurodexeinae, as closely related forms, have an elongated snout with numerous diastemas in the dentition, while the subfamily Lantianiinae , which is widely distributed in Asia, already had crescent-shaped ( bunoselenodonte ) tooth enamel cusps on the molars, which is actually only typical for ruminants .

Today there are three types:

Some fossil finds cannot be assigned exactly to one of the three species, such as the three Messel skeleton finds or some remains from the Geiseltal, but are considered to be affine to one of them. A significant increase in size from A. menieli to A. gabineaudi to A. maniai is remarkable , as well as the tooth enamel pattern of the posterior premolars slightly modified in the course of the tribal history .

The first scientific description of Aumelasia was in 1980 by Jean Sudre . He used finds from the site of Aumelas in the southern French department of Hérault , after which the genus is named. A maxillary fragment with the rearmost premolars and the three molars serves as the holotype (copy number USTL AUM 145). Sudre referred Aumelasia to the Dichobunidae, but the genus was meanwhile also considered a member of the Diacodexeidae , which unites the most basic artifacts.

literature

  • Thomas Lehmann and Irina Ruf: The appearance of the artifacts. In: Stephan FK Schaal, Krister T. Smith and Jörg Habersetzer (eds.): Messel - a fossil tropical ecosystem. Senckenberg-Buch 79, Stuttgart, 2018, pp. 285–291

Individual evidence

  1. ↑ a b c d e Jens Lorenz Franzen: Skeletons from Aumelasia (Mammalia, Artiodactyla, Dichobunidae) from Messel (M. Eocene, W. Germany). Courier Forschungsinstitut Senckenberg 107, 1988, pp. 309-321
  2. ↑ a b c d Jörg Erfurt and Hartmut Haubold: Artiodactyla from the Eocene brown coal of the Geiseltal near Halle (GDR). Palaeovertebrata 19 (1), 1989, pp. 131-160
  3. ↑ a b Thomas Lehmann and Irina Ruf: The emergence of the artifacts. In: Stephan FK Schaal, Krister T. Smith and Jörg Habersetzer (eds.): Messel - a fossil tropical ecosystem. Senckenberg-Buch 79, Stuttgart, 2018, pp. 285–291
  4. ↑ a b c d e Jessica M. Theodor, Jörg Erfurt and Grégoire Métais: The earliest Artiodactyls. In: Donald R. Prothero and Scott E. Foss (Eds.): The Evolution of Artiodactyls. Johns Hopkins University, Baltimore, 2007, pp. 32-58
  5. ↑ Jens Lorenz Franzen and Gotthard Richter: The primitive Unpaarhufer - loners in the undergrowth. In: S. Schaal and W. Ziegler (eds.): Messel - A shop window into the history of the earth and life. Frankfurt am Main, 1988, pp. 251-256
  6. ↑ Jens Lorenz Franzen: The first skeleton of a Dichobunid (Mammalia, Artiodactyla), recovered from Middle Eocene oil shale from the "Messel Pit" near Darmstadt (Germany, S-Hessen). Senckenbergiana lethaea 61 (3/6), 1980, 299-353
  7. ^ Métais Grégoire, Jianwei Guo and K. Christopher Beard: A new small dichobunid artiodactyl from Shanghuang (Middle Eocene, Eastern China): Implications for the early evolution of proto-selenodonts in Asia. Bulletin of Carnegie Museum of Natural History 36, 2004, pp. 177-197
  8. ↑ Jörg Erfurt: Taxonomy of the Eocene Artiodactyla (Mammalia) of the Geiseltal with special consideration of the genus Rhagatherium. Hallesches Jahrbuch für Geoswissenschaften B 17, 1995, pp. 47–58

Web links

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