Messelobunodon

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Messelobunodon
Skeleton of Messelobunodon

Skeleton of Messelobunodon

Temporal occurrence
Middle Eocene
47.4 to 46.3 million years
Locations
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Artiodactyla (Artiodactyla)
Dichobunidae
Dichobuninae
Messelobunodon
Scientific name
Messelobunodon
Franzen , 1980

Messelobunodon is an extinct today Paarhufergattung from the family of Dichobunidae that reference to some complete skeletons from the Messel Pit is detected and the Middle Eocene lived about 47 million years ago. The representatives of the genus were of rather small stature and had characteristically short front and long hind legs and, typical of early cloven-hoofed animals, an extraordinarily long tail. Based on fossil stomach remains, a preferred diet of soft plant material and mushrooms could be determined. According to reconstructions, Messelobunodon lived in dense forests as rather shy bush panties.

features

Messelobunodon was a comparatively small representative of the ungulates, which with a head-trunk length of around 42 cm was somewhat smaller than the almost equally old Amphirhagatherium . The characteristic features included the short forelegs, the distinctive upward curve of the back and the extremely long tail. The skull reached a length of around 10 cm. What was striking was its wedge-shaped outline with an elongated rostrum in side view . Under the slightly protruding nasal bone there was a relatively large nasal cavity, which reached at least the level of the first premolar . The eye window was located relatively far back in the skull, approximately at the level of the second and third molars, and with a diameter of 1.7 cm was not particularly large. The position of the eyes showed that the snout area was slightly more than half the length of the total skull. The lower jaw, which was about 7.6 cm long, was equipped with a long and flat bone body, a maximum of 1 cm high behind the last molar, and thus appeared rather delicate. The teeth matched the early higher mammals and had accordingly following dental formula : . The incisors were only small in size and wide in shape, and overall looked like a shovel. The also quite small canine , which resembled the incisors in the lower jaw, but had a bumpy shape in the upper jaw, was noticeable . Subsequently, there was a distinctive diastema of around 5 mm in length on the first, second and third premolars , and only then was a closed row of teeth formed. The molars as a whole had low crowns ( brachyodont ) and a cusp pattern consisting of tooth enamel ( bunodont ), with the cusps forming two parallel rows ( bilophodont ), only a third was formed on the last molar. This reached about 6 mm in length in the lower jaw and thus represented the largest tooth in the dentition. The upper molars were still missing one of the four main cusps (hypoconus). In construction of Kauoberflächen the molars was messelobunodon generalized rather like most early cloven-hoofed animals and resembled today by pigs , typical crescent-shaped ( selenodonbte ) Kauoberflächen emerged only later, especially with the advent of ruminants .

The body skeleton has largely been passed on in full. The spine comprised 7 cervical, 13 thoracic, 6 lumbar, at least 3 sacrum and 24 tail vertebrae. The tail, in particular, was around 30 cm long in relation to the length of the body and was very long compared to today's artifacts. Other special features can be found in the musculoskeletal system. The fore-limbs, which were rather short compared to the hind legs, were characteristic. The humerus reached about 8 cm in length, the ulna was only slightly shorter. The ulna and radius were roughly the same thickness, and all the bones of the foreleg were very slender. In contrast, the thigh bone was 10 cm long, the shin a little longer. The forelimbs each ended in five toes, a feature that no longer occurs in today's even-toed ungulates and refers to the original character of Messelobunodon . The middle three rays (II to IV) were developed the longest and had claw-like shaped fore phalanges. The hind legs each had only four rays with two strong middle toes (III and IV), which, in contrast to today's cloven-hoofed animals, were not fused together. They also ended in pointed, but much wider hooves. Likewise, unlike today's cloven-hoofed animals, the cuboid bone and the scaphoid bone were not fused at the foot .

Fossil record

Messelobunodon is a relatively rare fauna element of the Eocene , which mainly appeared in the middle level of this geological epoch about 47 million years ago and, according to current research, indicates the beginning of the local stratigraphic level Geiseltalium . It is known from some skeletal finds from the Messel mine in Hesse, one of which, the first found and on which the description of the genus is based, has survived almost completely, but has been slightly forgotten. A few finds also come from the Geiseltal in Saxony-Anhalt.

Paleobiology

There are indications of soft tissue mainly from the first Messel find, but this is not itself passed down, but rather traced by bacterial processes (bacteriography). Mainly in the back area an upwardly curved course can be recognized by the arrangement of the vertebrae, which was also developed in other early cloven-hoofed animals such as Amphirhagatherium . However, the shape of the snout, ears and tail are not known. Partly digested food residues could be observed in the stomach area . The investigations of the remains mainly revealed parts of mushrooms and already decomposed leaves, but also a few fruits . This suggests that Messelobunodon sought its food on the ground, possibly pawing its forelegs in half-rotted leaves where the mushrooms thrived. The front limbs, which are significantly shortened compared to the rear limbs, could have had an advantageous effect. Regardless of the remains of the stomach examined, however, the low-crowned molars with their hump-shaped chewing surfaces also show such a food specialization in soft plant material ( browsing ). When searching for food, the sense of smell was possibly used, which was quite well developed due to the long nasal region.

Overall, messelobunodon a relatively slender animal with its shorter front and longer hind legs in his habit other like old animals that about amphirhagatherium resembled and how this in the dense forest lived as Busch panties. The elongated rear limbs, the lower parts of which were longer than the upper ones, already show typical adaptations to faster locomotion. In addition, the development of the knee joint , but less so of the elbow joint , suggests an already pronounced parasagittal gait. However, the shorter forelegs are a rather primitive feature of the ungulates and indicate a not yet fully developed, fast-moving movement, in contrast to many more modern pair of ungulates with their longer front extremities. However, the heel bone was well developed and, in connection with the elongated foot bones, indicates a pronounced ability to jump, which reinforces Messelobunodon's character as a flight animal. However, based on the sizes of the ears and eyes, it cannot be concluded whether the animals were more active during the day or at night.

Systematics

Messelobunodon is a genus from the extinct family of the Dichobunidae , which is one of the earliest representatives of the ungulates . Within the family, the genus belongs to the subfamily of the Dichobuninae, which were slightly larger than their sister group , the Eurodexeinae . Dichobune and Aumelasia are closely related genera , the latter is also represented by fossil finds in the Messel pit . Altogether, Messelobunodon, together with other early representatives such as Diacodexis from the group of Diacodexeidae or Amphirhagatherium from the group of Choeropotamidae, represents a very archaic morphotype of the ungulates, which is characterized by short front and long hind legs. This morphotype suggests that the hitherto little known group of the artifacts may have had a more jumping locomotion.

The first description of Messelobunodon was in 1980 by Jens Lorenz Franzen on the basis of the first skeleton find from the Messel pit, which at the same time represents the holotype (specimen number SMF ME 510) and is kept in the Senckenberg Natural History Museum; This skeleton find was the first complete dichobunid known at the time. In the same year Franzen had already mentioned the generic name in a publication on the finds from the Geiseltal, as the printing of his writing with the first description had been postponed for technical reasons. The name Messelobunodon is derived from the site of the Messel pit and the Greek words βουνόν ( bounon "hill") and ὀδούς ( odoús "tooth"), which refer to the characteristic design of the bumpy chewing surface of the molar teeth. Only one species is recognized : M. schaeferi . Another species, M. ceciliensis , which was also described in 1980 using the skull of a young animal and other bone fragments from the Upper Middle Coal of the Geiseltal in Saxony-Anhalt, has been synonymous with M. schaeferi since 1989 . Further finds, including a skeleton from the Messel Pit, which was originally also placed with Messelobunodon , gave rise to the creation of the new genus Eurodexis in 1996 due to significant deviations and to assign M. ceciliensis as a type species.

literature

  • 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
  • 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. ↑ Heinz Tobien: On the osteology of Masillabune (Mammalia, Artiodactyla, Haplobunodontidae) from the Middle Eocene of the Messel fossil site near Darmstadt (S-Hessen, Federal Republic of Germany). Geological Yearbook Hessen 113, 1985, pp. 5-58
  2. ↑ a b c d e f Jens Lorenz Franzen: The first skeleton of a Dichobunid (Mammalia, Artiodactyla), recovered from Middle Eocene oil slates from the "Messel Pit" near Darmstadt (Germany, S-Hessen). Senckenbergiana lethaea 61 (3/6), 1980, 299-353
  3. ↑ a b c 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
  4. ↑ a b c 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
  5. ↑ Jörg Erfurt: Stratigraphic meaning of the Artiodactyla (Mammalia) in the Palaeogene of Europe. Jörg Erfurt and Lutz Christian Maul (eds.): 34th meeting of the working group for vertebrate palaeontology of the paleontological society - March 16 to March 18, 2007 in Freyburg / Unstrut. Halle, Saale, 2007, pp. 175-182
  6. ↑ a b Jörg Erfurt and Hartmut Haubold: Artiodactyla from the Eocene brown coal of the Geiseltal near Halle (GDR). Palaeovertebrata 19 (1), 1989, pp. 131-160
  7. ↑ G. Richter: Studies on the nutrition of Messelobunodon schaeferi (Mammalia, Artiodactyla). Senckenbergiana lethaea 61 (3/6), 1980, 355-370
  8. ↑ a b Jörg Erfurt: Reconstruction of the skeleton and the biology of Anthracobunodon weigelti (Artiodactyla, Mammalia) from the Eocene of the Geiseltal. Hallesches Jahrbuch für Geoswissenschaften, Series B, Supplement 12, 2000, pp. 57–141
  9. ↑ Jens Lorenz Franzen and Günter Krumbiegel: Messelobunodon ceciliensis n. Sp. (Mammalia, Artiodactyla) - a new Dichobunidae from the Middle Eocene fauna of the Geiseltal near Halle (Saale). Journal of Geological Sciences 8 (12), 1980, pp. 1553-1560
  10. ↑ Jens Lorenz Franzen: A second skeleton of Messelobunodon (Mammalia, Artiodactyla, Dichobunidae) from the "Messel Pit" near Darmstadt (Germany, S-Hessen). Senckenbergiana lethaea 64 (5/6), 1983, 403-445
  11. ↑ 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

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