Buxolestes
- Germany ( Messel and the Geisel ) and France ( Bouxwiller )
Buxolestes is a now extinct species insectivore -like animals from the group of Pantolestidae. The representatives of the genus lived primarily in the Middle Eocene, 48-41 million years ago and are of several, including many complete skeletons from the Messel pit, but also finds from the Geisel and from Bouxwiller known in France. The skeleton of Buxolestes is rather primitive, so that the animals are characterized by a curved ridge path and a very long tail. But he shows specific adaptations to a partly aquatic ( semi- aquatic ), but also partly underground grave border ( fossoriale ) lifestyle. Ecologically, the representatives of Buxolestes took then a niche today's otters. Based on fossilized stomach remains were fish and small vertebrates, but also plant material be detected as food leftovers, so that Buxolestes probably analogous to today martens and foxes used a generic eat everything diet. The first description of Buxolestes was 1970.
Description
Buxolestes was a small to medium sized, insectivore -like animal, and had a head-body length of 36-46 cm. The Higher for early mammals characteristic, extremely long tail measure 24 to 36 cm and was about as long as the hull. Another typical feature introduced the bulged fuselage spine dar. The skull had lengths from 7.1 to 9.3 cm. He was compact and had thus tends to be high as long. The same applies to the rostrum, this was also characterized by a large nose inner space between the nose and the middle jawbone. The nose itself was thin and significantly extended to the rear, so that it reached to the height of the orbit. The eye socket was wide open to the rear. The paired frontal bone had a small head crest, while the zygomatic arches curved either up or relative just ran. The cantilevered to the rear occiput had a very strong bead as a point of attachment of the neck muscles as well as strong joint ends ( condyles ) of the cervical spine.
The mandible was built massive and 4.9 to 6.9 cm long. The strong bone body reached about 1.1 cm height in the region of the first molar. The teeth included the full number of teeth of the early higher mammals, the dentition formula was therefore: . The incisors were characterized by unequal sizes. That was in the lower dentition, the second, in the upper of the first and third enlarged, the latter had its conical shape more like a canine ( caniniform ). The canines were significantly developed and also designed conically pointed. The lower pointed to the inside of a distinctive groove, but it was not as well developed as in related genera. Both to the incisors and the posterior teeth was each a smaller diastema, so that the canine was free. The rear teeth formed a closed row of teeth. The premolars showed up on the rear clear deviations from the molars and therefore were not or only slightly molarisiert. They pointed to the Kauoberfläche but in each case a plurality of pointed tooth enamel cusps. The lower molars were five, the three higher, a group formed, which were separated by a channel of the two lower ( tribosphenischer tooth structure ). The upper molars also had several pointed cusps, which were grouped on the outside, the inside of the tooth was surrounded by a wide tooth enamel belt ( cingulum ). The length of the molar varied to 4.8 mm, the width was slightly greater than approximately 6 mm. The posterior molar showed partially some dilations. The entire row of teeth from the canine to the last molar was in large species up to 4 cm.
The body skeleton is well known by a number of fossil finds. The spine consisted of 7 cervical, 13 thoracic, 5-6 lumbar and 22 to 28 caudal vertebrae, the number of sacral vertebrae is unknown, but was closely related genera such as Pantolestes at 3 Especially at the 6 anterior caudal vertebrae were conspicuous broad transverse processes. In addition, they were each in size with 1.5 cm in length. The vortex behind it have become increasingly smaller and only reported rudimentary appendages on. The front and rear extremities had a balanced aspect ratio and were overall relatively short, however, had the rear a bulkier expression. The humerus measured up to 5.4 cm and was slightly curved shank course. The bones of the forearm were not connected, the Elle reached more than 6 cm and showed a large upper joint ( olecranon ). The robust femur with the strong swivel head had a well-trained third trochanter and was 7 cm long, tibia a little longer. This therefore provided the longest bones in the skeleton dar. tibia and fibula were firmly adherent. Front and hind legs ended in each five-pointed feet. The middle three beams each possessed (II to IV), the longest On the embossing and here again the third. Overall, the front and hind feet showed no strong specializations, such as significant extensions or reductions of metapodials or phalanges. However, the end members of the toes were pointed convergent and thus give to the existence of long claws, there were also slight indentations on the surface.
Fossil finds
Finds of Buxolestes mainly come from the Middle Eocene, about 48 to 43 million years and are largely known only from Europe. These three nearly complete skeletons from the Messel Pit near Darmstadt, which have been handed down in the lateral position. A fourth skeleton from the same locality was in the recovery but damaged and is therefore less well preserved. All finds from Messel are assigned to the lower portion of the Mitteleozäns. From a crushed skull has also been reported from the Geisel valley near Halle. He comes from the local Upper Middle coal, which represents the upper portion of the Mitteleozäns. Other discoveries come from Bouxwiller in Alsace in France. These include not only some isolated teeth and longer tooth rows also several complete mandibular rami. Your age has approximately a middle position between the fossils of Geiseltal and those of the Messel Pit.
Paleobiology
In general physique, especially the short compared to the trunk limbs, the long tail and the meat food pointing teeth structure corresponds Buxolestes a modern otter ( Lutra lutra ) from the marten family. One of the otters comparable, semi aquatic lifestyle can be seen from the skeletal morphology. The kragende back occiput, the powerful approaches of the cervical spine and the small head crest refer to a well-developed, short neck muscles, which indicates a very moving head. This high mobility was necessary in order to keep its head above water while swimming. On the other hand, the strong projections on Atlas, the first cervical vertebra, the abdominal was particularly badly designed and made for increased lateral mobility of the head. This is mainly for hunting advantageous if the prey moves out laterally. An upper and lower jaw distinct foramina, openings in the bone, is formed, such as the mental foramen or the foramen are infraorbital. This provides a very sensitive snout is assumed and the presence of whiskers around the muzzle likely. However, the foramen infraorbital not reached the size comparable to the otter, so that the vibrissae in Buxolestes were not so pronounced pronounced. Perhaps the representatives of Buxolestes were characterized diurnal or hunted in predominantly clear water.
Also at the tail, certain adjustments indicate a partly floating lifestyle. The six large eddy the base of the tail with its broad transverse processes that occupy a third of the tail length, can be found according to the otter again, uses the tail as a drive element. The there accreting muscles enable a powerful up-and- slide and lateral meandering of the tail. From the Messel also remains of soft tissue by bacteria traced ( Bacteriographie ) and thus survived. They give a rounded, not flattened tail again, as it also shows the otter today. In contrast, the limbs show a few special adaptations to swimming. The femur is not shortened, which would be regarded as a special adaptation to swimming, because the resulting shortened lever function would facilitate the paddles on the foot. An extension of the phalanges as in sea otters is not detectable. The hind foot was being restrained by the coalescence of the fibula to the tibia in his lateral movements. The severity of the heel bone, especially the heel cusp, but enabled a powerful return movement of the foot. The unconnected bones of the forearm indicate a floating forefoot. The strongly developed upper joint of the ulna also allows for a significant extension of the foreleg. This is typical of animals with a grave end of life, which Buxolestes was consequently capable to go underground in search of food or to dig shelters. On a grave activity could continue to indicate the long middle finger, which is typical among other things, for the fossorial living armadillos, as well as the already mentioned good return movement of the foot for pushing away the excavation.
Frequently Buxolestes is considered predatory live animal specializing in fish food. Provide evidence in addition to the general structure of the teeth molars with their very pointed cusps. However, the typical for predators and the extinct Creodonten crushing scissors missing teeth in the back. A first, almost complete, but slightly damaged skeletal finds from the Messel pit also contained legacies from the gastro -intestinal tract. These included numerous, fragmented long bones and vertebrae remains small vertebrates, but also thin bony plates, which can be considered as fish scales, but most were not conclusive enough. One of only 2.2 mm long jaw fragment with remains of the dentition proved to be a remnant of Atractosteus, a frequently occurring in Messel fish shape. Another skeleton Fund the same locality contained far only indefinable bone material. From the stomach contents of two other individuals of Messel, however, only vegetable scraps, as seeds and fruits could be determined. These findings from the digestive tracts seem to contradict themselves accordingly. But since today's predators, especially from the group of dogs and raccoon eat partly heaped plant foods, can the traditional gastric residual Buxolestes on one and possibly seasonal indicate varying diet. Overall, a similar way of life is due to these findings for Buxolestes as in today's otters, which he occupied its ecological niche in the Middle Eocene. This need of Buxolestes how Wighart Koenigswald 1980 stressed, "but to have been reached neither the same elegance while swimming nor the extent of the sensory performance as Lutra. ".
System
Buxolestes is a genus of the family of Pantolestidae. These include primitive insectivore -like animals that are detected from the Middle to the Upper Paleocene to Lower Oligocene in North America and Eurasia, and temporarily in the transition from Paleocene to Eocene occurred in northern Africa. Both the inner and the other relationships of Pantolestidae are poorly understood. Often the Pantolestidae are considered members of the subordination of Pantolesta within the order of Cimolesta. In the closer relationship of Buxolestes Palaeosinopa and Pantolestes from the lower and Middle Eocene of North America and Pagonomus can be made from the Paleocene of Europe. The latter is also handed out Walbeck in Saxony- Anhalt. The origin of the Pantolesta is partially seen in the Leptictida that are already known from the Upper Cretaceous and are close to the present-day insectivores.
Today, three types are known:
- P. minor Pfretzschner, 1999
The first description of Buxolestes was made by Jean -Jacques Jaeger in 1970. Basis for forming a plurality of tooth finds from Bouxwiller. The holotype ( specimen number: BCHS 100) includes a left mandible with dentition from canine to the last molar tooth, the foremost premolar is incomplete. It is located in the Natural History Museum of Basel. The name Buxolestes refers on one hand to the locality Bouxwiller, on the other hand, the similarity and close relationship to the North American Pantolestes.