Eurotamandua
| Eurotamandua | ||||||||||||
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Eurotamandua joresi , fossil in the Senckenberg Research Institute |
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| Temporal occurrence | ||||||||||||
| Middle Eocene ( Lutetium ) | ||||||||||||
| 47.4 to 46.3 million years | ||||||||||||
| Locations | ||||||||||||
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Germany ( Messel Pit , Geiseltal ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Eurotamandua | ||||||||||||
| Stork , 1981 | ||||||||||||
Eurotamandua is an extinct genus from the order of the Pholidota , to which the pangolins (Manidae)living today alsobelong. The first fossil was found in 1974 in the Messel mine near Darmstadt and was first scientifically described seven years later. Other finds are known from the Geiseltal . All remains found are assigned to the Middle Eocene and are therefore around 47 million years old. In the opinion of the firstperson describingit, it was an extinct representative of the anteater (vermilingua), making Eurotamandua the oldest known fossil of this group of animals, which is otherwise only found in South America. However, renewed investigations into phylogenesis make a closer relationship with the pangolins likely. Characteristic features of Eurotamandua are the tubular and toothless snout and the typical structure of the front limbs with an extended middle finger.
description
Eurotamandua achieved a total length of about 86 cm based on a complete skeleton find, of which about 36 cm was accounted for by the tail. Overall, it was a massive and powerful animal with numerous adaptations to a specialized way of life. The skull was 8.8 cm long and was relatively small compared to the body. In the side view he had a smooth forehead line, the skull profile sloped slightly only in the area of the rostrum . The rostrum was also elongated in a tubular shape and thus resembled today's pangolins and anteaters . The elongated nasal bone measured 3.7 cm and thus took up about 42% of the total length of the skull. The side edges showed a curved design, while the rear end clearly protruded into the frontal bone . Below the nasal bone which put directly means jawbone of which was extremely short at 0.8 cm in length. The upper jaw did not form part of the orbital margin . Unlike today's pangolins and anteaters, the zygomatic arch was fully developed but poorly developed. The lower jaw was 6.5 cm long and had the shape of a long, narrow clasp. The symphysis showed a slight broadening and a slightly downward course in the side view. Missing alveoli in the upper and lower jaw indicate that Eurotamandua was completely edentulous. In the front section, however, there was a slight thickening of the bone, which resembles the mandibular spur of the pangolin.
The postcranial skeleton is well known, but the number and exact appearance of the vertebrae are only certain for the posterior part of the body. The spine consisted of 7 cervical, at least 9 thoracic, 4 lumbar, 5 sacrum and 24 tail vertebrae. In the well-preserved caudal spine, only the foremost vertebrae had functioning vertebral arches and broad transverse processes, the rear ones were cylindrical and simply designed. The length of the vertebrae decreased continuously towards the rear, from 1.8 cm in the front tail area to 0.8 cm in the rear. The front and rear extremities were roughly equally long and strong. The humerus measured up to 7 cm and had a short, strong structure. The ulna and radius were not connected. In addition, the ulna, which reached up to 8.5 cm in length, had an upper joint ( olecranon ) that was quite extensive at 2.4 cm . The thigh bone was up to 8 cm long and was also robust. The third trochanter, typical of pangolins and anteaters, took up about 30% of the lateral bone shaft, but was not particularly prominent. The tibia and fibula were also free, both were characterized by straight diaphyses. The former bone was 7 cm in length, the latter 6.1 cm in length. The front and rear feet each had five rays, but the front foot was significantly larger. The central ray (III) of the hand, which was clearly elongated, especially on the terminal phalanges, the length of which was 2.7 cm, appeared striking. The clearly convex curvature of the terminal phalanges indicates that they were originally equipped with strong claws, the attachment of which is indicated by a clear groove on the side of the phalanx.
Fossil finds
The most important fossil from Eurotamandua , a complete, on its side lying skeleton of a nearly full-grown animal and according to Kenneth D. Rose one of the most beautiful and vexing of Messel fossils ("one of the most beautiful and annoying of the Messel fossils"), became found in 1974 by Gerhard Jores in the northern area of the Messel pit , the so-called Long Slope, in grid squares F 6/7. It is extremely well preserved, but individual disarticulations can be found in the front part of the body on the spine and the upper section of the forelimbs. In the following, the preparation was partly carried out by the discoverer himself. Other finds come from the lower coal of the Geisel valley near Halle in Saxony-Anhalt. These include isolated remnants of the right front extremity with the humerus and ulna . Both sites belong to the Middle Eocene (locally stratigraphically dated in the section Lutetium ) and are about 47 million years old.
Paleobiology
Overall, Eurotamandua is a strong animal. The preservation of the forefoot does not yet allow any interpretation of the locomotion, so a plantigrade gait is possible as well as folding down the claws on the palm, as is known in pangolins and anteaters. The strong reduction of the outermost finger beam (V) makes the latter quite likely. The hind feet, on the other hand, were aligned with a sole passage. The long, slender tail with a short anterior section consisting of more highly differentiated vertebrae most likely did not serve as a supporting or grasping organ. The structure of the skull with the tubular snout and the toothless bite, but also the extended claw of the middle finger can be a strong specialization in state-forming insects such as ants and termites include ( Myrmecophagie ), similar to the in today's pangolins and similarly for the Anteaters of Case is. The sharp claws of the forefoot, especially the middle toe, were used to break open the insect burrows. Due to its good quality, the Messel fossil allows not only a very detailed examination of skeletal elements but also a determination of the stomach contents. Layers of chitin membranes were found in the stomach , but there are no typical head capsules or dentition structures. Cross-scaled cuticles predominated, some of which are strongly folded and resemble the abdomina of today's termites, but it is not possible to clearly identify them as remnants of termites or ants. In addition, a larger proportion of wood structures was found in a cemented matrix that cannot be determined in more detail, which is comparable to the nest building materials of today's tree termites with pieces of wood in hardened saliva. These plant residues are to be understood as “by-catch” of the Eurotamandua's food intake , which, as in today's pangolins and anteaters, probably took place with a long, sticky tongue. In addition, there are also numerous grains of sand from the stomach contents . Today's pangolins and anteaters often swallow sand in order to chew food in the stomach that has not been chewed due to the toothless mouth.
Systematics and research history
Eurotamandua an anteater?
Eurotamandua was first scientifically described in 1981 by Gerhard Storch using the complete skeleton from the Messel pit (specimen number SMF Me 80/24) . In its first description, Storch referred to Eurotamandua as a genus to the anteaters (Vermilingua) and to a more precise relationship with the great anteaters ( Myrmecophaga ) and the Tamanduas ( Tamandua ), which make up the family of the Myrmecophagidae . The scientific generic name Eurotamandua takes into account both the assumed close relationship to the Tamanduas and the location of the fossil in Europe . The reasons for the close relationship with the anteaters were, among other things, the formation of xenarthric joints (secondary joints or xenarthrals) on the articular processes (zygapophyses) of the posterior thoracic and anterior lumbar vertebrae, which was recognized at the time, which is one of the central features of the secondary articular animals and thus also of the anteater also the drawn-down symphysis of the lower jaw and the shape of the front limbs, in addition the typical development of the hearing and the special, strongly extended backward structure of the palate are indicated. In general, the physique was similar to that of the tamanduas native to South America, which are known to be less specialized compared to the other anteaters and live both on the ground and in trees. Further similarities to the pangolins were noted, but these were largely only considered primitive features.
According to its first description, Eurotamandua would have been the oldest known anteater at the time, at 47 million years old, and the only one ever discovered outside of America. The anteaters comprise a highly specialized group within the sub-joint animals (xenarthra). The phylogenetic relationship of the secondary animals was not always clearly clarified in the past. Originally, these were referred to together with the aardvark (Orycteropodidae) and the pangolins (Manidae) in 1798 by Georges Cuvier in the order of the toothless (Edentata). Although the concept of the Edentata was questioned as early as the second half of the 19th century and largely abolished at the beginning of the 20th century, some researchers carried out both the pangolins (within the Pholidota as a superordinate group) and the Collateral articulated animals as core components of the Edentata, so among others in the first description of Eurotamandua .
Biogeographical controversies
The secondary articulated animals are widespread today on the American double continent. Its origin lies in the Paleocene of South America, but it may go back to the Upper Cretaceous . It was not until the middle Pliocene , when a land bridge was built on the Isthmus of Panama , that some representatives also reached Central and North America. Fossil taxa of the secondary articulated animals originally described from Europe, Asia or Africa later turned out to belong to other groups, such as scaled lizards or pangolins and their relatives. Various paleogeographical explanations have been used to establish Eurotamandua's presence in Europe and its relationship with the anteaters. Immigration via North America was seen as an alternative, but a more favored one was found via Africa, which only separated from South America in the Upper Cretaceous around 80 to 100 million years ago. The emergence of the early groups of mammals, including the sibling animals, is dated to the same time, so that Eurotamandua could have descended from a very early anteater line. This should then have inhabited parts of the later African continent, whereupon the ancestors of Eurotamandua reached Europe via the Tethys in the late Cretaceous or early Tertiary . Further phylogenetic investigations on the basis of morphological characteristics of recent and fossil taxa from 1998 partially supported this thesis and placed Eurotamandua at the base of the anteater or alternatively with the inclusion of the Pholidota at the base of all tooth arms (pilosa), the common group of anteaters and sloths ( Folivora). Analyzes from the same year, however, led to the fact that Eurotamandua was excluded from the direct relationship of the secondary animals, but was referred to the specially newly created order Afredentata as their only member. An origin from the secondary articulated animals was considered probable, as well as a closer relationship to the palaeanodonta was assumed. These extinct, once ground-dwelling animals are, according to today's view, close to pangolins.
Present position
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Internal systematics of the Pholidota according to Gaudin et al. 2009 and Gaudin 2010
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The view above of Eurotamandua's close kinship with the anteater was viewed with skepticism in the 1990s. Some phylogenetic studies instead suggested a relationship with the palaeanodonts. By molecular genetic analysis has been recognized during this time also that the pangolins and Xenarthra are not closely related to each other. Thus, the secondary articulated animals form one of the four great main lines of the higher mammals , which stand opposite the other three (collectively as Epitheria ) as a sister group . The pangolins (order Pholidota) together with the predators (Carnivora) form the higher-level taxon Ferae , which is part of the main line of Laurasiatheria . The external similarities of pangolins and secondary articulated animals, but especially of the anteaters - such as the tubular snout, the toothless jaw, the long, sticky tongue and the shape of the front legs - go back to convergent developments that arose due to the similar way of life of the two animal groups.
Renewed anatomical examinations of the pangolins living today and their fossil relatives from 2009 now showed that Eurotamandua should be placed in the order of the Pholidota, but no precise family assignment was made. Reasons for the reassignment are given with the misinterpretation of the xenarthric joints - these later turned out to be the result of the restoration work - the special structure of the forelegs and the forefeet and, above all, the different arrangement of the articular surfaces on the metacarpal and finger bones differ significantly from the anteaters despite the general similarities. The Pholidota form together with the extinct Palaeanodonta, which are known from the Palaeogene of North America and Europe, the superordinate group of the Pholidotamorpha . Within the Pholidota, Eomanis and Euromanis are the closest relatives of Eurotamandua ; These two genera were also found in the Messel pit and together form the basis of the development of pangolin relatives. They still have numerous original features that they have in common with the palaeanodonta, including a C-shaped central jawbone , a small bone rib at the rear end of the jaw and some special characteristics of the forelegs such as the elongated end members of the forefeet. The appearance of the primitive representatives of the Pholidota in Messel leads to the assumption that the entire group may have developed in Europe and only later spread to Asia and Africa. In some cases, Euromanis , which so far is only known from a skull-less skeleton and was originally described as Eomanis krebsi , was considered a young of Eurotamandua and thus identical to it. This was contradicted, however, and marked differences, especially on the rear legs, were pointed out. At present, only one valid species is known, Eurotamandua joresi , which was named by Gerhard Storch, who first described it in 1981, after the discoverer of the Messel skeleton, Gerhard Jores.
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
- Gerhard Storch: Eurotamandua joresi, a Myrmecophagid from the Eocene of the "Messel Pit" near Darmstadt (Mammalia, Xenarthra). Senckenbergiana lethaea 61 (3/6), 1981, pp. 247-289
Individual evidence
- ↑ a b c d e f Gerhard Storch: Eurotamandua joresi, a Myrmecophagid from the Eocene of the "Messel Pit" near Darmstadt (Mammalia, Xenarthra). Senckenbergiana lethaea 61 (3/6), 1981, pp. 247-289.
- ↑ a b c Frederick S. Szalay and Friedemann Schrenk: The Middle Eocene Eurotamandua and a Darwinian phylogenetic Analysis. Kaupia 7, 1998, pp. 97-186.
- ↑ a b c 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 Gerhard Storch and Hartmut Haubold: Additions to the Geiseltal Mammalian Faunas, Middle Eocene: Didelphidae, Nyctiteriidae, Myrmecophagidae. Palaeovertebrata 19 (3), 1989, pp. 94-114.
- ↑ a b Kenneth D. Rose: The importance of Messel for interpreting Eocene mammalian faunas Holarctic. Palaeobiology and Palaeoenvironments 92, 2012, pp. 631-647.
- ↑ Gotthard Richter: Studies on the nutrition of Eocene mammals from the Messel fossil site near Darmstadt. Courier Forschungsinstitut Senckenberg 91, 1987, pp. 1-33.
- ^ Gerhard Storch and J. Habersetzer: Choans and accessory bulla tympanica in recent Vermilingua and Eurotamandua from the Eocene of Messel (Mammalia: Xenarthra). Journal of Mammals, 56, 1991, pp. 257-271.
- ↑ a b Inés Horovitz, Gerhard Storch and Thomas Martin: Ankle structure in Eocene pholidotan mammal Eomanis krebsi and its taxonomic implications. Acta Palaeontologica Polonica 50 (3), 2005, pp. 545-548 ( PDF full text ).
- ↑ a b Frédéric Delsuc and Emmanuel JP Douzery: Recent advances and future prospects in xenarthran molecular phylogenetics. In: Sergio F. Vizcaíno and WJ Loughry (eds.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 11-23.
- ^ Wighart von Koenigswald: Paleogeographical relationships of the vertebrate fauna from the ancient Tertiary fossil deposit Messel near Darmstadt. Geological Yearbook Hessen 109, 1981, pp. 85-102.
- ↑ Gerhard Storch: The ancient tertiary mammal fauna of Messel - a paleobiogeographical puzzle. Naturwissenschaften 71, 1984, pp. 227-233.
- ↑ Timothy J. Gaudin and Daniel G. Branham: The Phylogeny of the Myrmecophagidae (Mammalia, Xenarthra, Vermilingua) and the Relationship of Eurotamandua to the Vermilingua. Journal of Mammalian Evolution 5 (3), 1998, pp. 237-265, doi: 10.1023 / A: 1020512529767 .
- ↑ a b c Timothy J. Gaudin, Robert J. Emry and John R. Wible: The Phylogeny of Living and Extinct Pangolins (Mammalia, Pholidota) and Associated Taxa: A Morphology Based Analysis. Journal of Mammalian Evolution 16, 2009, pp. 235-305.
- ↑ Timothy J. Gaudin: Pholidota. In: Lars Werdelin and William Joseph Sanders (eds.): Cenozoic Mammals of Africa. University of California Press, Berkeley, London, New York, 2010, pp. 599-602.
- ↑ Kenneth D. Rose: Eurotamandua and Palaeanodonta: convergent or related? Paläontologische Zeitschrift 73 (3/4), 1999, pp. 395-401.
- ↑ Frédéric Delsuc, Francois M. Catzeflis, Michael J. Stanhope and Emmanuel JP Douzery: The evolution of armadillos, anteaters and sloths depicted by nuclear and mitochondrial phylogenies: implications for the status of the enigmatic fossil Eurotamandua. Proceedings of the Royal Society of London B 268, 2001, pp. 1605-1615.
- ^ Gerhard Storch: Fossil Old World "edentastes" (Mammalia). Senckenbergiana biologica 83 (1), 2003, pp. 51-60.
- ↑ Gerhard Storch and Thomas Martin: Eomanis krebsi, a new pangolin from the Middle Eocene of the Messel pit near Darmstadt (Mammalia: Pholidota). Berliner Geoscientific Abhandlungen E 13, 1994, pp. 83–97.
Web links
- The Paleobiology Database Eurotamandua