Lesmesodon

Skeleton of Lesmesodon

Germany ( Messel )

Lesmesodon is an extinct genus from the order of Creodonta, carnivorous mammals ( Carnivora ) are more closely related to the predators. It lived in the middle Eocene, around 47 million years ago and is only known from the Messel Pit near Darmstadt. Proved is the genre for several, partly complete skeletons of young animals, together with some almost adult animals, fully grown individuals are not known. These represent rather small representatives of Creodonta that were adapted to a soil-dwelling life because of the physique.

Description

Lesmesodon is a small to medium-sized representatives of Creodonta, the date is only young animals and nearly adult individuals with known just completely trained permanent dentition of two different types. Subadult representatives of the smaller form reached a head-body length of 20 to 25 cm, the larger up to 45 cm. There was also a long tail, which reached approximately the length of the hull. The body weight varied between less than 1 and approximately 6 kg, so the genus reached the size of a modern domestic cat. The weight could turn even slightly higher compared to today's predators, since the Creodonta had different body proportions. Typical of Creodonta were the big head and the shorter limbs. The skull of the smaller form measure up to 6.9 cm in length, to the rather clasp shaped zygomatic arches, the width up to 3.8 cm. The nose was thin and stretched back to the level of the second molar. Between the end connected to the nasal bone and the upper jaw means jawbone was a small recess, which started the lower canine. The eye window was above the first molar, the leading edge was formed by the lacrimal bone. The upstream infraorbital foramen opened at the roots of the last premolar. At the contact seam of the paired parietal a small head crest was designed.

The lower jaw was slender and straight and below the last premolar good 0.5 cm high, the articular ends reached about four times the height. The teeth showed with three incisors, one canine, three premolars and three molars each a pine bough over the early higher mammals hardly reduced number of teeth, the dental formula was therefore: . Whether the foremost premolar was actually already regressed or failed very early or very late broke is not yet fully understood. The incisors showed a small, pen -like shape and were partially flattened front and rear, only the upper third was significantly increased. The canines appeared large and curved like a sickle, the upper exceeding the lower of size. To the rear teeth was a short, 2-3 mm long diastema. The Kauoberflächen the premolars and molars featured pointed tooth enamel cusps. The premolars were long and narrow and were not in a closed series. The largest teeth were the second and third molar with approximately 0,5 cm in length, which acted as the main crushing scissors in the dentition. The length of the lower teeth from the canine to the last molar was about 3.3 cm.

The body skeleton is occupied by several fossil finds. The spine consisted of 7 cervical, 13-14 thoracic, 7 lumbar, an unknown number of sacral and 27 caudal vertebrae. The limits at the thoracic vertebrae ribs were laterally flat and bent as a whole only moderate. The large anterior caudal vertebrae characterized strong spine and transverse processes, to the rear vortex became smaller and leaner. The limbs were relatively short. The humerus reached at smaller Lesmesodon forms 3.4 to 4.2 cm in length and had a strongly elongated shape. Radius and ulna were not fused together, at the 2.7 -cm-long cubit was a relatively broad upper joint ( olecranon ) with forward-facing position. On the shaft of the femur a third trochanter was designed as a muscle attachment point. The whole bones measured up to 4.2 cm and was thus longer than the tibia 3.3 cm. Front and hind legs ended in five beams with a solid design midstream (III). The outer beams (I and V), however, were the shortest. The hind exceeded the forefoot by a third in length. So had the metacarpal III with the smaller representatives of 1.2, the metatarsus 1.8 cm length. The end members of the toes had a slightly curved shape in the side view and the front end had small incisions, indicating that the claws were a little retractable.

Fossil finds

Finds of Lesmesodon are only known from the Messel Pit near Darmstadt, which is dated to the middle Miocene epoch, about 47 million years ago. In addition to a skull with parts of the body skeleton and some isolated teeth were still a part of the skeleton and also a nearly complete in the lateral position detected with very well-preserved replication of the soft tissues, especially the tail and the back body portion. All these findings are not yet assign adult ( juvenile ) individuals. Other fossil remains have so far received no detailed description, but underneath there is a sub - adult individual who previously represented the only the juvenile stage of the animals.

Paleobiology

In general, the Creodonta recorded over today's carnivores ( Carnivora ) with a large head and short limbs from. At some of the Messel finds itself still had the soft tissues demonstrate that however do not get even, but traced by bacteria ( Bacteriographie ). In particular, the rear body portion and the tail are documented. Thus, the tail was probably built especially bushy and provided with long hair, while this turned out much shorter on the body back. However, the fur on the belly side again consisted of longer hair. The ears are not traced, here it can be assumed that these were small and were hidden in the fur.

The dentition of Creodonta similar to the predators. A striking difference is however is the location of the crushing scissors that significantly further back was the Creodonta in the dentition and distributed to the three rearmost molars. The construction of the molars with pointy Zahnschmelzhöckerchen refers to an animal diet at Lesmesodon, which probably partly invertebrates were consumed. A skeleton of a young animal of only 25 cm in length contained bone and tooth remains an iguana as food residues. However, the skeleton of the Creodonten itself shows strongly rotated broken ribs and a position of the limbs to the body, so that it is as ausgespiehener food residue of a boa constrictor, possibly by Palaeopython, interpreted, thus the animal was himself a victim of birds of prey.

In the locomotion Lesmesodon was more generalized and adapted to the soil, for which address some postcranial features. So referenced by the rather rounded shoulder blade towards a little schnellläufige movement. The front-facing upper joint of the ulna is indeed typical of some tree dwellers, but also for plantigrade, can thus also partly a grave lifestyle are adopted. For a plantigrade run way also speaks of the construction of the front and rear feet with her towards the inner rays ( I) larger outer rays ( V). Other characteristics such as the upper arm bone contradict a climbing lifestyle. Even though the tail was relatively long, but too short to serve as a grasping organ when climbing. However, giving the foremost caudal vertebrae with its distinctive spine and transverse processes of a strong musculature, so that the tail was probably used in running to the preservation of balance.

System

Lesmesodon is a genus of the extinct family of Hyaenodontidae, which in turn form part of the also extinct order of Creodonta. The Creodonta, often somewhat misleadingly referred to as " Urraubtiere ", form the sister group of the present-day carnivores ( Carnivora ) within the parent group of the ferae and passed over a long period from the Paleocene more than 56 million years ago until the middle Miocene epoch, about 11 million years ago. Of the predators, the Creodonta ( usually 1 to 3 molar ) differ by a further back in his mouth crushing scissors, which also einbezog more teeth, and significantly shorter limbs. Within the Hyaenodontidae Lesmesodon is referenced in the subfamily Proviverrinae. These are considered more primitive representatives and probably represent the sister group to all other members of the family. Too close related genera include about Proviverra and Leonhard Tina, both forms are detected from the about the same old reference Geiseltal in Saxony- Anhalt, but each reached significantly larger body shapes.

There are now recognized in two ways:

• L. behnkeae Morlo & Habersetzer, 1999
• L. Horn edingeri Spring, 1982

Here is L. behnkeae significantly larger than L. edingeri, the latter is also the type species.

The first description of Lesmesodon was made in 1999 by Michael Morlo & Jörg Habersetzer the basis of a complete skeleton of a juvenile animal from Messel. In the genus but also other skeletal remains were included, discovered one of which in 1974 and 1982 had been described as belonging to Proviverra. Another came in subsequent to the fore and also received an assignment to Proviverra. The holotype of the type species ( copy number IRScNB IG 26533 ) includes a skull print with the dentition and parts of the body skeleton. It is preserved today in Brussels. The genus name Lesmesodon consists of the term " Lesmes ", an anagram for " Messel " and the Greek word for " tooth" ( ὀδούς Odous ) together.