Microgale macpheei
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| Goodman , Vasey & Burney , 2007 |
Microgale macpheei is an extinct species of mammal belonging to the genus Kleintenreks within the Tenreks family. It is only known about two skull fragments from a cave site in the extreme southeast of Madagascar . In terms of anatomical features, the representatives resembled today's short-tailed small tenrek , but were on average larger and more powerfully built. Together with Microgale macpheei , remains of other members of the Kleintenreks came to light in the cave. These can be assigned to various modern forms, none of which can be found in the immediate region. The cave site is located in a transition area from the humid forest landscapes of the east to the dry areas of the western Madagascar. The age of the finds dates between 1600 and 2700 years. It is possible that the extinction of Microgale macpheei and the disappearance of the other Kleintenreks from the region coincide with the drying up of the landscape during this period. At the same time, humans appeared on the island for the first time, and in their wake numerous strange fauna elements. Microgale macpheei was first described scientifically in 2007. It is the only known, recently extinct representative of the Kleintenreks.
features
Microgale macpheei is so far only known about individual skull fragments, each of which is missing the rear sections. In most of the morphological and anatomical features there is the greatest similarity to the short-tailed small tenrek ( Microgale brevicaudata ) and the grandidier small tenrek ( Microgale grandidieri ). Overall, Microgale macpheei was built more robustly. The rostrum ended at the front rather blunt and not as pointed as the Grandidier-Kleintenrek. The zygomatic arch was not fully formed as the other tenrecs. In the area of the anterior arch attachments, the skull width was 8.6 mm, while it averaged 7.8 and 7.9 mm in both the Grandidier Kleintenrek and the short-tailed Kleintenrek. The length of the palatine bone measured 9.4 to 9.7 mm in Microgale macpheei , with the two similar Kleintenre maps it was significantly shorter with 8.1 and 7.6 mm respectively. In comparison, the teeth of Microgale macpheei were much more robust. Only the rear teeth with the premolars and molars , which were larger overall and had more extensive chewing surfaces, have survived in full . Based on the number of alveoli , the structure of the upper dentition typical of the Kleintenreks can be determined with three incisors , one canine and three premolars and three molars per jaw arch. The three molars combined had a total length of 3 mm, which in turn is longer than the Grandidier Kleintenrek and the short-tailed Kleintenrek with 2.7 and 2.6 mm respectively. Also deviating from the short-tailed Kleintenrek but more or less identical to the Grandidier-Kleintenrek, there were no diastemas between the premolars . Further significant differences can be found in the construction of the second premolar (P3), which in Microgale macpheei was more simply structured and had a nail-shaped main protuberance (protoconus). In the Grandidier-Kleintenrek this showed widening towards the tongue side. At the rear premolar (P4) another main cusp (Paraconus) in Microgale macpheei had a more delicate structure. The molars were broad overall. Their zalambdodonte chewing surface structure with three main cusps corresponded to that of the other Kleintenreks. Differences to the Grandidier Kleintenrek and the short-tailed Kleintenrek occurred in different forms of individual shear surfaces, such as the ectostyle and the mesostyle, which were of different lengths in Microgale macpheei , but were about the same length in the Grandidier Kleintenrek.
Finds and find area
The Microgale macpheei fossil finds were discovered in the Andrahomana Cave , which is located southwest of Tolagnaro in the extreme southeast of Madagascar. The cave is in the Eolianit embedded -Aufschlüssen the cliff that here rise up to 100 m and sediment deposits in the output of the cold periods of the Pleistocene formed. The cave roof itself has collapsed, leaving numerous openings to the surface that act as natural traps. The cave was first visited in 1899 by the Austrian naturalist Franz Sikora, who discovered the bones of numerous lemurs , such as Archaeolemur or Hadropithecus , during initial investigations . In the following decades there were repeated research stays, among others by Martin François Geay in the first decade of the 20th century or by Raymond Decary in the 1920s. The most recent field research took place at the beginning of the 21st century. The investigations revealed an extremely rich fossil material comprising several thousand bones. It is made up of remnants of lemurs, but also of rodents , bats , tenre-kitties , predators and cloven-hoofed animals . There are also numerous species of birds , including elephant birds such as Aepyornis and Mullerornis , as well as reptiles and amphibians . According to radiocarbon dating, the finds cover the period of the last 8700 years; the most recent data, together with finds of domestic dogs and zebu , fall into the phase of the first human colonization of the island. The remains of the skull of Microgale macpheei also belong to this age range . This is evident from several radiocarbon measurements on the lower jaws of the Petter big foot mouse , which were recovered in the underlying and overlying layers. The age data obtained range from 790–410 BC. BC to AD 150–390 (each calibrated C14 years ).
Systematics
Microgale macpheei is a kind from the genus of microgale ( Microgale ) within the family of tenrecs (Tenrecidae). The Kleintenreks also belong to the subfamily of the Reistenreks (Oryzorictinae), which in turn also includes the rice burrowers ( Oryzorictes ) and the representatives of the genus Nesogale . With more than 20 recent species, the genus forms the most diverse member of the Tenreks, due to some morphological features they are also considered to be relatively original within the family. According to molecular genetic data, its formation dates back to the Lower Miocene around 16.8 million years ago, after which it was severely split. Today the animals are mainly to be found in the humid forests of eastern Madagascar, only a few species have also developed the drier landscapes of the western part of the island. Today's Kleintenreks show adaptations to different ways of life, which range from partially underground digging to above-ground living to tree-climbing variants. Both morphologically and genetically there are various related groups within the genus. The anatomical features speak for a closer relationship of Microgale macpheei with the short-tailed Kleintenrek ( Microgale brevicaudata ) and with the Grandidier-Kleintenrek ( Microgale grandidieri ).
The first scientific description of Microgale macpheei was made in 2007 by a research team led by Steven M. Goodman . They used two skull fragments that were recovered in the Andrahomana Cave in the extreme southeast of Madagascar. The holotype (copy number FMNH 191249) comprises the complete front skull of a presumably adult animal. The rostrum is largely completely preserved up to the point of the parietal bone . In addition, the complete front teeth with the incisors, the canine and the front premolar (P2) are missing, as well as the left second premolar (P3). The piece was discovered in early July 2003, the site was in the northernmost end of the cave chamber and comprised an excavation area of about 25 m². Along with this, another front part of the skull came to light, which is also damaged on the molars. Both fossil finds were associated with mandibular remains and parts of the body skeleton, which most likely also come from small tenreks. However, it is unclear whether these are remains of the same species. In the first description, Goodman and colleagues compared their new species with representatives of the short-tailed lesser tenrec from southwest and western Madagascar. The population from the southwest, namely that from the Onilahy River , was later referred to the new species Microgale grandidieri in 2009 . The specific epithet macpheei refers to Ross DE MacPhee , who, among other things, carried out pioneering studies on the Kleintenreks and thus made outstanding contributions to researching these endemic animals.
meaning
It is in Microgale macpheei around the first and only known extinct representatives of microgale. The other forms described on the basis of subfossil material, such as Microgale breviceps and Microgale decaryi, could subsequently be associated with more recent representatives (with the short-tailed Kleintenrek and the large long-tailed Kleintenrek ( Microgale principula )). The Andrahomana Cave is located in a transition area from the dry areas of the western to the wetlands of the eastern part of the island, which is caused by its position on the west side and thus in the slipstream of the nearby Anosyenne Mountains . As a result, the landscape is characterized by thorny bush vegetation. The fauna found in the cave includes inhabitants of both the damp eastern and the drier western part of the island and thus roughly reflects the current situation on site. With respect to the microgale the cave barg also residues of other members of the genus, such as by short-tailed Kleintenrek, from little long-tailed Kleintenrek ( Microgale longicaudata ) from Gnomkleintenrek ( Microgale pusilla ) or from Nasolo-Kleintenrek ( Microgale nasoloi ). Since most of the Kleintenreks inhabit the tropical rainforests of eastern Madagascar, this is also partly assumed for Microgale macpheei . This assumption is supported by the occurrence of the Petter big foot mouse in the same time horizon, which today lives in western Madagascar, but is found there in less dry forest landscapes. None of the other found representatives of the Kleintenreks is still at home in the area around the Andrahomana cave. The disappearance of numerous fauna elements may be accompanied by a drying up of the region, which occurred in the last two to three thousand years. At this time, however, humans also arrived on the island, as a result of which the house rat and house mouse also immigrated. What is striking in this context is the increase in finds of these neozoa in the upper layers of the Andrahomana Cave, while at the same time the number of fossil remains of the native fauna is declining. It must be emphasized that the decline in numerous and the subsequent extinction of some of the Malagasy endemics affected not only large animals, but also often smaller vertebrates. In the first description of Microgale macpheei , however, the authors speculated that the species may still be alive today, as a possible refuge was Malahelo at the foot of the Ambatotsirongorongo mountains east of the Andrahomana cave, as there are even more humid forests here. However, the area has not been explored very much, preliminary field investigations there have so far provided no evidence of small tenreks.
literature
- Steven M. Goodman, Natalie Vasey and David A. Burney: Description of a new species of subfossil shrew tenrec (Afrosoricida: Tenrecidae: Microgale) from cave deposits in southeastern Madagascar. Proceedings of the Biological Society of Washington 120 (4), 2007, pp. 367-376
Individual evidence
- ↑ a b c d e f Steven M. Goodman, Natalie Vasey and David A. Burney: Description of a new species of subfossil shrew tenrec (Afrosoricida: Tenrecidae: Microgale) from cave deposits in southeastern Madagascar. Proceedings of the Biological Society of Washington 120 (4), 2007, pp. 367-376
- ↑ a b c d Link E. Olson, Z. Rakotomalala, KBP Hildebrandt, HC Lanier, Christopher J. Raxworthy and Steven M. Goodman: Phylogeography of Microgale brevicaudata (Tenrecidae) and description of a new species from Western Madagascar. Journal of Mammalogy 90 (5), 2009, pp. 1095-1110
- ^ A b Steven M. Goodman, Nathalie Vasey and David A. Burney: The subfossil occurrence and paleoecological implications of Macrotarsomys petteri (Rodentia: Nesomyidae) in extreme southeastern Madagascar. Comptes Rendus Palevol 5, 2006, pp. 953-962
- ^ A b D. A. Burney, N. Vasey, LR Godfrey, Ramilisonina, WL Jungers, M. Ramarolahy and L. Raharivony: New Findings at Andrahomana Cave, Southeastern Madagascar. Journal of Cave and Karst Studies 70 (1), 2008, pp. 13-24
- ^ A b Steven M. Goodman and William L. Jungers: Extinct Madagascar. Picturing the island's past. University of Chicago Press, 2014, pp. 1–206 (pp. 65–73)
- ↑ Kathryn M. Everson, Voahangy Soarimalala, Steven M. Goodman and Link E. Olson: Multiple loci and complete taxonomic sampling resolve the phylogeny and biogeographic history of tenrecs (Mammalia: Tenrecidae) and reveal higher speciation rates in Madagascar's humid forests. Systematic Biology 2016 doi: 10.1093 / sysbio / syw034
- ^ RDE MacPhee: The Shrew Tenrecs of Madagascar: Systematic Revision and Holocene Distribution of Microgale (Tenrecidae, Insectivora). American Museum Novitates 2889, 1987, pp. 1-45
- ^ JF Eisenberg and Edwin Gould: The Tenrecs: A Study in Mammalian Behavior and Evolution. Smithsonian Institution Press, 1970, pp. 1-138
- ↑ Aristide Andrianarimisa, Vonjy Andrianjakarivelo, Zafimahery Rakotomalala and Mirana Anjeriniaina: Vertébrés terrestres of fragments forestiers de la Montagne d'Ambatotsirongorongo, site dans le Système of Aires de Madagascar protégées de la Région Anosy, Tolanaro. Malagasy Nature 2, 2009, pp. 30-51