Lesmesodon
| Lesmesodon | ||||||||||||
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Lesmesodon skeleton |
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| Temporal occurrence | ||||||||||||
| Middle Eocene ( Lutetium ) | ||||||||||||
| 47.4 to 46.3 million years | ||||||||||||
| Locations | ||||||||||||
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Germany ( Messel Pit ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Lesmesodon | ||||||||||||
| Morlo & Habersetzer , 1999 | ||||||||||||
Lesmesodon is an extinct genus from the order of the Hyaenodonta , carnivorous mammals that areclosely relatedto the predators (Carnivora). It lived in the middle Eocene around 47 million years ago and is only known from the Messel mine near Darmstadt. The genus has been proven through several, partly complete skeletal finds of young animals together with some almost fully grown animals; fully grown individuals have not survived. These represent rather small representatives of the Hyaenodonta, which were adapted to a soil-dwelling way of life due to their physique.
description
Lesmesodon is a small to medium-sized representative of the hyaenodonta , but so far only known from young animals and almost adult individuals with fully developed permanent teeth of two different species. Subadult representatives of the smaller form reached a head-trunk length of 20 to 25 cm, the larger up to 45 cm. There was also a long tail that reached about the length of the trunk. The body weight varied between 300 g for smaller and around 1.5 kg for larger representatives. The genus thus reached the size of today's dwarf mongoose or fanaloka . The weight could also be a little higher compared to today's predators because the hyaonodonta had different body proportions. The large head and the shorter limbs were typical of Hyaenodonta. The skull of the smaller form measured up to 6.9 cm in length, on the rather clasp-shaped zygomatic arches the width was up to 3.8 cm. The nasal bone was slender and stretched back to the level of the second molar . There was a small recess between the upper jaw, which is connected to the nasal bone, and the central jawbone , which accommodated the lower canine . The eye window was above the first molar, the front edge was formed by the tear bone . The anterior infraorbital foramen opened at the roots of the last premolar . A small crest was formed at the contact seam of the pair of parietal bones .
The lower jaw was slender and straight and under the last premolar a good 0.5 cm high, the joint ends were about four times the height. The teeth showed three incisors , one canine, three premolars and three molars depending pine bough one against the early higher mammals hardly reduced number of teeth and tooth formation was thus: . Whether the anterior premolar had actually already regressed or failed particularly early or broke through very late has not yet been conclusively clarified. The incisors had a small, pin-like shape and were partially flattened at the front and back, only the upper third was significantly enlarged. The canines appeared large and curved like a sickle, the upper one larger than the lower one. There was a short, 2 to 3 mm long diastema to the posterior dentition . The chewing surfaces of the premolars and molars were characterized by sharp enamel cusps . The premolars were long and narrow and not in a closed row. The largest teeth were the second and third molar, each around 0.5 cm long, which acted as the main breaking scissors in the dentition. The length of the lower row of teeth from the canine to the last molar was about 3.3 cm.
The body skeleton is documented by several fossil finds. The spine consisted of 7 cervical, 13 to 14 thoracic, 7 lumbar, an unknown number of sacrum and 27 tail vertebrae. The ribs attached to the thoracic vertebrae were flat on the sides and only moderately curved overall. The large anterior caudal vertebrae were characterized by strong spinous and transverse processes, and towards the rear the vertebrae became smaller and slimmer. The limbs were relatively short. In smaller lesmesodon forms, the humerus reached a length of 3.4 to 4.2 cm and was strongly elongated. The ulna and radius were not fused together; the 2.7 cm long ulna had a relatively extensive upper joint ( olecranon ) with a forward-facing position. A third trochanter was formed as a muscle attachment point on the shaft of the femur . The entire bone measured up to 4.2 cm and was therefore longer than the shin at 3.3 cm. Front and rear legs each ended in five rays with a solid central ray (III). The outer rays (I and V), on the other hand, were the shortest. The rear foot exceeded the forefoot by a third in length. The metacarpus III was 1.2 cm long in the smaller representatives and the metatarsus 1.8 cm long. The end links of the toes had a slightly curved shape when viewed from the side and had small incisions at the front end, which indicate that the claws were somewhat retractable.
Fossil finds
Finds of Lesmesodon are so far only known from the Messel Pit near Darmstadt , which is dated to the Middle Miocene around 47 million years ago. Almost half a dozen individuals were discovered. In addition to a skull with parts of the body skeleton and some isolated teeth, there is also a partial skeleton and an almost complete one in a lateral position with very well preserved traces of the soft tissue , especially on the tail and in the back of the body. All of these finds have not yet been assigned to adult ( juvenile ) individuals. Further fossil remains have not yet received a detailed description, but among them there is a sub- adult individual who is the only one that does not represent the animals' adolescence.
Paleobiology
In general, the Hyaenodonta were distinguished from today's predators (Carnivora) by a large head and shorter limbs. In some of the Messel finds, the soft tissue could still be demonstrated, although this is not actually preserved, but traced by bacteria (bacteriography). Especially the rear part of the body and the tail are documented in this way. The tail was probably built particularly bushy and provided with long hair, while these were significantly shorter on the back of the body. However, the fur on the belly side consisted of longer hair. The ears are not drawn, here it can be assumed that these were small and were hidden in the fur.
The teeth of the hyaenodonta are similar to those of predators. A striking difference, however, is the position of the crushing scissors, which in the hyaenodonta was significantly further back in the dentition and was distributed over the second molar in the upper and the third molar in the lower jaw. The structure of the molars with the pointed enamel cusps refers to an animal diet in Lesmesodon , whereby invertebrates were probably also consumed in some cases . A skeleton of a young animal only 25 cm long contained remains of bones and teeth from an iguana as food remains . However, the skeleton of the hyaenodont itself shows severely broken ribs and a position of the limbs rotated around the body, so that it is interpreted as the spit out of food from a strangler snake, possibly from a palaeopython , with which the animal itself became the victim of a predator.
In locomotion, lesmesodon was more generalized and adapted to the ground, which is supported by some postcranial features. The rather rounded shoulder blade indicates a movement that is not very fast. The forward-facing upper joint of the ulna is typical for some tree dwellers, but also for sole walkers , and a partially digging way of life can also be adopted. The structure of the front and rear feet with their outer rays (V) which are larger than the inner rays (I) also speaks for a plantigrade running style. Other characteristics, such as the humerus, contradict a climbing lifestyle. The tail was also relatively long, but too short to be used as a grasping organ when climbing. However, the foremost caudal vertebrae with their distinctive spinous and transverse processes indicate a strong musculature, so that the tail was probably used to maintain balance while running.
Systematics
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Internal systematics of the Hyaenodonta, especially the Proviverrinae according to Borths et al. 2016
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Internal systematics of the Hyaenodonta, especially the Proviverrinae according to Solé & Mennecart 2019
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Lesmesodon is a genus from the extinct subfamily of the Provoverrinae , which in turn form part of the also extinct order of the Hyaenodonta . Originally, the members of the Hyaenodonta were led within the Creodonta , which often, somewhat misleadingly, also bore the designation "primal predators" in German. The Creodonta were regarded as the sister group of today's carnivores within the parent group of the Ferae and existed for a long period from the Paleocene more than 56 million years ago to the Middle Miocene about 11 million years ago. The Creodonta differ from the predators in that they have crushing shears (mostly molars 1 to 3) further back in their mouths, which also included more teeth and significantly shorter limbs. However, the Creodonta proved to be non- monophyletic and were therefore divided into the group of Hyaenodonta and Oxyaenodonta . The Proviverrinae are considered to be rather primitive representatives of the Hyaenodonta and together with the Limnocyoninae represent the sister group to all other members of the group (sometimes the Provoverrinae are also managed within their own parent taxon , the Proviverroidea). In contrast, a more recent study from 2019 sees the Proviverrinae as being more closely related to the Hyaenodontidae . Proviverra from the Geiseltal site in Saxony-Anhalt, which is roughly the same old, is one of closely related genera , but it achieved a significantly larger body shape. Two types are recognized today:
- L. behnkeae Morlo & Habersetzer , 1999
- L. edingeri Springhorn , 1982
It is L. behnkeae significantly greater than L. edingeri , at the same time the latter is the type species.
The first description of lesmesodon was made in 1999 by Michael Morlo & Jörg Habersetzer basis of a complete skeleton of a juvenile animal from Messel. Other skeletal finds were also included in the genus, one of which was discovered in 1974 and described in 1982 as belonging to Proviverra . Another came to light in the following and was also assigned to Proviverra . The holotype of the type species (copy number IRScNB IG 26533) comprises a skull imprint with the teeth and parts of the body skeleton. It is now kept in Brussels . The generic name Lesmesodon is made up of the term "Lesmes", an anagram for "Messel", and the Greek name for "tooth" ( ὀδούς odoús ).
literature
- Gregg F. Gunnell, Thomas Lehmann, Irina Ruf, Jörg Habersetzer, Michael Morlo and Kenneth D. Rose: Ferae - animals that eat other animals. In: Stephan FK Schaal, Krister T. Smith and Jörg Habersetzer (eds.): Messel - a fossil tropical ecosystem. Senckenberg-Buch 79, Stuttgart, 2018, pp. 271–283
- Michael Morlo and Jörg Habersetzer: The Hyaenodontidae (Crerodonta, Mammalia) from the lower Eocene (MP 11) of Messel (Germany) with special remarks on new x-ray methods. Courier Forschungsinstitut Senckenberg 216, 1999, pp. 31–73
Individual evidence
- ↑ a b c d Gregg F. Gunnell, Thomas Lehmann, Irina Ruf, Jörg Habersetzer, Michael Morlo and Kenneth D. Rose: Ferae - animals that eat other animals. In: Stephan FK Schaal, Krister T. Smith and Jörg Habersetzer (eds.): Messel - a fossil tropical ecosystem. Senckenberg-Buch 79, Stuttgart, 2018, pp. 271–283
- ^ A b c d e Rainer Springhorn: New predators (Mammalia: Creodonta et Carnivora) from the lutetium of the Messel pit (Germany. Palaeontographica A 179 (4-6), 1982, pp. 105-141
- ↑ a b c d e Rainer Springhorn: A new individual from Proviverra edingeri (Mammalia, Creodonta) from the Middle Eocene by Messel. Senckenbergiana lethaea 68 (5/6), 1988, pp. 371-391
- ↑ a b c d e f g h i j Michael Morlo and Jörg Habersetzer: The Hyaenodontidae (Crerodonta, Mammalia) from the lower Eocene (MP 11) of Messel (Germany) with special remarks on new x-ray methods. Courier Forschungsinstitut Senckenberg 216, 1999, pp. 31–73
- ↑ Michael Morlo: New original predator from Messel provides unique O information. Natur und Museum 128 (7), 1998, pp. 208-211
- ↑ a b c Michael Morlo, Gregg F. Gunnell and Krister T. Smith: Mammalian carnivores from Messel and a comparison of non-volant predator guilds from the middle Eocene of Europe and North America. In: T. Lehmann and SFK Schaal (eds.): The World at the Time of Messel: Puzzles in Palaeobiology, Palaeoenvironment and the History of Early Primates. 22nd International Senckenberg Conference Frankfurt am Main, 15th - 19th November 2011 Frankfurt am Main, 2011, pp. 120–212
- ↑ Michael Morlo, Stefan Schaal, Gerald Mayr and Christina Seiffert: An annotated taxonomic list of the Middle Eocene (MP 11) Vertebrata of Messel. Courier Forschungsinstitut Senckenberg 252, 2004, pp. 95-108
- ↑ Michael Morlo, Renate Rabenstein, Stefan Schaal and Jörg Habersetzer: Diet of non-flying Messel tetrapods: Direct vs. indirect evidence. Journal of Vertebrate Paleontology 22 (3), 2002 (suppl.), P. 90A
- ^ Rainer Springhorn: Carnivorous Elements of the Messel Fauna. Courier Forschungsinstitut Senckenberg 107, 1988, pp. 291-297
- ↑ a b Matthew R. Borths, Patricia A. Holroyd and Erik R. Seiffert: Hyainailourine and teratodontine cranial material from the late Eocene of Egypt and the application of parsimony and Bayesian methods to the phylogeny and biogeography of Hyaenodonta (Placentalia, Mammalia). PeerJ 4, 2016, p. E2639; doi: 10.7717 / peerj.2639
- ↑ a b Floréal Solé and Bastien Mennecart: A large hyaenodont from the Lutetian of Switzerland expands the body mass range of the European mammalian predators during the Eocene. Acta Palaeontologica Polonica 64, 2019 doi: 10.4202 / app.00581.2018
- ↑ Michael Morlo, Gregg Gunnell, and P. David Polly: What, if not nothing, is a creodont? Phylogeny and classification of Hyaenodontida and other former creodonts. Journal of Vertebrate Paleontology 29 (3 suppl), 2009, p. 152A
- ↑ Floréal Solé: New proviverrine genus from the Early Eocene of Europe and the first phylogeny of Late Paleocene-Middle Eocene hyaenodontidans (Mammalia). Journal of Systematic Paleontology 11, 2013, pp. 375-398
- ↑ Kenneth D. Rose: The beginning of the age of mammals. Johns Hopkins University Press, Baltimore, 2006, pp. 1–431 (pp. 122–126)
