Eomanis
| Eomanis | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Skeleton of Eomanis waldi |
||||||||||||
| Temporal occurrence | ||||||||||||
| Middle Eocene | ||||||||||||
| 47.4 to 46.3 million years | ||||||||||||
| Locations | ||||||||||||
|
Germany ( Messel Pit ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name of the family | ||||||||||||
| Eomanidae | ||||||||||||
| Stork , 2003 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Eomanis | ||||||||||||
| Stork , 1978 | ||||||||||||
Eomanis is an extinct mammal from the Eomanidae family and is one of the oldest indubitable relatives of the pangolins (Manidae), of which eight species still live in Africa and Asia. It was a small animal, about half a meter long, that had typical adaptations to a soil life and possibly built earthworks. In its habitus , Eomanis showedtypical characteristics that refer to state-forming insects as food. However, found food residues suggest a plant-based diet so far. Fossil finds come only from the Messel Pit and date to the Middle Eocene 47 million years ago. Thegenus was first described in 1978.
features
Eomanis reached a head-trunk length of 25 to 27 cm, the tail length was about 22 cm and thus about 88% of the length of the rest of the body. In its overall habit it resembled today's pangolins (Manidae), but the physique was somewhat more plump and the limbs shorter and stockier. The skull was 7.3 cm long and long and narrow with a wedge-shaped design in side view. He had a flat skull roof. The very narrow nasal bone was 2.9 cm long and around 40% of the total length of the skull, while the frontal bone measured 1.9 cm. The zygomatic arches were not fully formed, as in today's pangolins. The orbit was not delimited from the temporal pit, which indicates that the eyes must have been very small. The lower jaw had a length of 5 cm, it was elongated and built like a clasp. At the end of the joint it reached a maximum height of 1.2 cm. Due to the lack of alveoli , it can be assumed that no teeth were formed, as is the case with pangolins today.
The body skeleton is well known. The spine consisted of 7 cervical, 12 thoracic, 5 lumbar, 4 sacrum and 24 tail vertebrae. The cervical spine was short and the individual vertebral bodies only formed low bone ridges as spinous processes . The lumbar spine was also clearly stocky with very short vertebrae, which made the trunk appear markedly shortened. The caudal vertebrae had no appendages, especially in the rear, and were generally rather small and narrow in shape. The humerus had a robust shape, the ulna and radius were not fused together. The ulna reached a length of 5 cm and had an extensive upper joint ( olecranon ) which alone took up 1.6 cm of the entire length of the bone. The thigh bone was also strongly formed and measured up to 6 cm. The noticeable third trochanter, a muscle attachment point, was located high up on the bone shaft near the upper joint. As in the arms, the bones of the lower leg were not fused together. The shin was up to 5 cm long and had a columnar shaft, as was the fibula , which was almost straight and quite slim. Arms and legs ended in five-pointed hands and feet with short and wide phalanges . The central ray (III) in particular was significantly elongated. The fingers and toes ended in sharp claws, but the respective end links were not split.
Today's pangolins have a characteristic scale dress, to which they owe the common name "pine cone" due to the roof-tile-like arrangement of the individual scales . The scales consist of keratin , which is rarely preserved in fossil form. However, a skeleton that was found has remnants of scales in the area of the thigh bone and suggests that Eomanis had similar armor. The scales were quite small and pointed back with the pointed end. The surface had fine longitudinal grooves, while the edge was surrounded by a small border. Overall, the scales of Eomanis roughly corresponded to those of today's pangolins.
Fossil finds
The only known fossil remains of Eomanis come from the Messel pit near Darmstadt . The entire site is placed in the Middle Eocene and is around 47 million years old. At least five almost complete skeletons are known, including one from a young animal. It is noticeable that a large part of the skeletons were found lying on their backs and more rarely on their prone positions, which differs from the lateral position of mammals found in Messel (with the exception of the bats ). The reason for this is probably the rather squat physique, and the formation of a curved scale armor, which was relatively heavy, provided a regulation in the still water environment of the former Maarsee, usually with the convex surface pointing downwards .
Paleobiology
Overall, Eomanis had a strong body with short limbs and was reminiscent of today's pangolins , but has a comparatively shorter and somewhat clumsier body and a larger skull, which may be related to a less specialized way of life. The front legs in particular were characterized by a short and wide humerus , which offered plenty of space for muscle attachment points. The very extensive upper joint ( olecranon ) of the ulna is comparable to that of today's burrowing mammals such as the recent scale animals but also the armadillos , which suggests a similar way of life. This is also indicated by the extended middle finger and the broad phalanges. Eomanis probably lived as a digger who looked for food underground and built protective structures against predators . However, the relatively thin tail suggests that it did not function as a support when digging, climbing or straightening up, as is the case with pangolins or analogously with anteaters and armadillos. For this reason, Eomanis probably lived as a pure ground animal and moved there plantigrad . The hind legs also show some special features. In Eomanis, for example, the third trochanter is clearly offset in the direction of the upper joint end and not, as in most specialized graves, towards the middle of the bone shaft. As a result, the rear extremities were less stretchable and not very suitable for digging, so they were probably not used to push away the excavation. The cervical spine was also very short and wide, making the head less mobile.
Despite individual anatomical differences, Eomanis appears to have been strongly adapted in its habitus to a way of life like that of today's pangolins. These feed mainly on insects that form colonies such as ants and termites ( myrmecophagia ). Certain features of the skull also show that Eomanis was obviously a fully developed Myrmecophage. These include the elongated, partly tubular snout, the loss of teeth and the clasp-shaped, narrow shape of the lower jaw, but also the only small muscle attachment surfaces, which indicate reduced masticatory muscles. Such traits developed independently several times and occur not only in pangolins but also in anteaters. Both groups eat food via a long, flexible and sticky tongue, which, due to the structure of the skull, can also be accepted in Eomanis . In contradiction to these clearly myrmecophagous adaptations, however, the food residues found in some of the Messel skeletal remains in the gastrointestinal area. Some of the remains consist of grains of sand that are not found in the Maar Sea deposits at Messel. Sand is also ingested by today's pangolins and is used to crush the food that has not been chewed due to the lack of teeth. In addition, however, only a few insect remains have been detected, especially the chitin sheaths . In addition, however, there are large amounts of plant material such as leaf remains with well-preserved cell tissue and herbaceous stems. One possibility was that a large part of the insect remains in the stomach area had been broken down by formic acid - today's representatives of the scale ants have up to 70% formic acid as defense secretion - which, however, did not decompose the plant remains, which could not be confirmed in experiments. On the other hand, it was assumed that it was only apparent food residues that had accumulated secondarily in the stomach area of the animals lying on their backs and that they sagged into the soft tissue after the decomposition of the soft tissue. But here, too, there are some taphonomic problems, because then, among other things, the plant remains in the various Eomanis skeletons would have had to be stored in a freshly crushed state and not as disintegrated detritus , which would have been more the case. For this reason, the researchers of the finds assumed that the food of Eomanis consisted of small-cut parts of the plant of leaf-cutting ants , whereby the high-energy insects were taken in as "bycatch", and that the pangolin precursors did not adapt to ants and termites until later formed. However, this model does not explain the clearly myrmecophage traits formation in Eomanis . This is why other scientists see Eomanis as a fully developed insect eater, which only accidentally swallowed plants, with the insect remains, for unknown reasons, barely or not at all. So far, the dominance of the plant material in the food remains has not been clarified.
Systematics
|
Internal systematics of the Pholidota according to Gaudin et al. 2009 and Gaudin 2010
|
Eomanis is a genus of the family of Eomanidae, in turn, to order the Pholidota heard of the living today pangolins (Manidae) are assigned as the sole extant family. Together with the extinct Palaeanodonta , which are limited to the paleogene of North America and Europe, they form the superorder Pholidotamorpha . Originally Eomanis was considered an extinct member of today's pangolins and their oldest undoubted representative, but later it was spun off into the related Patriomanidae , which included all fossil representatives of the pangolin. It was not until 2003 that the Patriomanidae were assigned to the Eomanidae family due to the resulting paraphyletic origin.
Close relatives of Eomanis include Euromanis and Eurotamandua , both of which have also been handed down from the Messel mine . The two genera together with Eomanis are at the base of the development of the Pholidota and still have numerous original features that they have in common with the Palaeanodonta and from which they may have developed. These include 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 links of the forefeet. For a long time there was a systematic controversy as to whether Eurotamandua is related to Eomanis , since the former was originally identified as a representative of the anteater - it would thus be the only European representative of this group of animals, otherwise known only from South America, and the oldest at all. This controversy was also caused by the fact that pangolins and anteaters have great physical similarities and were long thought to be closely related. It was only through more recent molecular genetic studies that it was possible to establish that this similarity is based solely on convergence .
One species is known, Eomanis waldi , which was first described by Gerhard Storch in 1978 . The holotype (specimen number SMF Me 84) is a complete skeleton that lies on its back. It is privately owned by the finder, a cast is in the Senckenberg Research Institute in Frankfurt am Main . The genus name Eomanis refers to the age of the finds ( Eocene ) and the relationship to the pangolins (the genus Manis within the Manidae). The species name waldi honors the finder Rudolf Wald, who made the find available for research purposes. Another species, Eomanis krebsi , also introduced by Storch in 1994, is now considered a member of the genus Euromanis , which was first described in 2009.
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
- TS Kemp: The Origin & Evolution of Mammals. Oxford University Press, Oxford 2005. ISBN 0-19-850761-5
- Gerhard Storch: Pholidota, pangolin, pine cone. In: Wilfried Westheide and Reinhard Rieger (eds.): Special zoology. Part 2: vertebrates or skulls. Gustav Fischer Verlag, Stuttgart et al. 2003, ISBN 3-8274-0900-4 , pp. 510-514.
Individual evidence
- ↑ a b c d Gerhard Storch: Eomanis waldi, a pangolin from the Middle Eocene of the "Messel Pit" near Darmstadt (Mammalia: Pholidota). Senckenbergiana lethaea 59 (4/6), 1978, pp. 503-529
- ↑ a b c Gerhard Storch and Thomas Martin: Eomanis krebsi, a new pangolin from the Middle Eocene of the Messel mine near Darmstadt (Mammalia: Pholidota). Berliner Geoscientific Abhandlungen E 13, 1994, pp. 83–97
- ^ A b Wighart von Koenigswald, Gotthart Richter and Gerhard Storch: Evidence of horn scales in Eomanis waldi from the "Messel Pit" near Darmstadt (Mammalia: Pholidota). Senckenbergiana lethaea 61 (3/6), 1981, pp. 291-298
- ↑ a b c Gerhard Storch: A pangolin from the Messel pit - on the paleobiology of a Middle Eocene manid. Natur und Museum 108 (10), 1978, pp. 301-307
- ↑ 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 Gotthard Richter: Pangolins - 50 million years ago hardly different from today. In: S. Schaal and W. Ziegler (eds.): Messel - A shop window into the history of the earth and life. Frankfurt am Main, 1988, pp. 203-207
- ↑ Kenneth D. Rose: The beginning of the age of mammals. Johns Hopkins University Press, Baltimore, 2006, pp. 1-431 (pp. 204-210)
- ^ 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 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
- ^ Frederick S. Szalay and Friedemann Schrenk: The middle Eocene Eurotamandua and a Darwinian phylogenetic analysis. Kaupia 7, 1998, pp. 97-186
- ^ Gerhard Storch: Fossil Old World "edentates" (Mammalia). Senckenbergiana biologica 83 (1), 2003, pp. 51-60
- ↑ Kenneth D. Rose: The importance of Messel for interpreting Eocene Holarctic mammalian faunas. Palaeobiology and Palaeoenvironments 92, 2012, pp. 631-647
- ↑ Gerhard Storch: Eurotamandua joresi, a Myrmecophagid from the Eocene of the "Messel Pit" near Darmstadt (Mammalia, Xenarthra). Senckenbergiana lethaea 61, 1981, pp. 503-529
- ↑ 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
