Somali gerbil

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Somali gerbil
Systematics
Superfamily : Mice-like (Muroidea)
Family : Long-tailed mice (Muridae)
Subfamily : Gerbils (Gerbillinae)
Tribe : Ammodillini
Genre : Ammodillus
Type : Somali gerbil
Scientific name of the  tribe
Ammodillini
Pavlinov , 1981
Scientific name of the  genus
Ammodillus
Thomas , 1904
Scientific name of the  species
Ammodillus imbellis
( de Winton , 1898)

The Somali gerbil or walo ( Ammodillus imbellis ) is a species of gerbil and the only species in the genus Ammodillus . It was described by William Edward de Winton in 1898 as Gerbillus imbellis . Due to peculiar characteristics, it is often placed in a separate Ammodillini tribe .

This little gerbil inhabits steppe and desert areas in the Horn of Africa in low density . It is about four inches long without a tail. The over-body-length, otherwise sparsely hairy tail has a tassel at the end . The soles of the feet are hairless and have a grainy, flaky surface structure. The fur is reddish fawn on the top and white on the underside.

It differs from other recent gerbils by the construction of the skull and the teeth. Characteristic are two preserved, original minor cusps of the lower molars in connection with the highly specialized construction of the masticatory apparatus and the tympanic membranes . Specializations are the shape of the palate and the absence of the muscular process of the lower jaw .

Body features

Exterior

The Somali gerbil is a small gerbil with large eyes and a long tail . This is mostly sparsely hairy, but has a tassel with eight to ten millimeters long, slender hair in the rear third. The hind paws are narrow and the claws of the front paws are relatively well developed. The paws are sparsely hairy and the hairless soles and pads have a scale-like , granular surface structure. The comparatively sparsely hairy top of the tail and the hairless soles of the feet represent typical developments within gerbils.

The fur is reddish fawn on top. The hair on the back and the sides of the body have black tips, but that of the sides to a lesser extent. Therefore, the sides of the body are clearer and lighter colored fawn and sharply outlined. The undercoat is dark slate gray. The hair above the eyes, that of the cheeks and the front of the front legs have fawn-colored tips. There are distinct white spots above the eyes and behind the ears. The front and rear paws, chin, cheeks and underside are white. The tail is darker on top than below and the hair of the tassel is brownish.

Kingdon (1997) gives the head-torso length of the Somali gerbil at 105 to 110 millimeters, the tail length at around 130 to 150 millimeters and the body weight at around 40 to 60 grams. According to Funaioli (1971), the head-trunk length is 85 to 106 millimeters and the tail length 134 to 160 millimeters. Drake-Brockman (1910) gives the head-torso length of a living specimen as 106 millimeters, the tail length as 144 millimeters, the hind foot length as 27 millimeters and the ear length as 25 millimeters.

skull

The skull of the Somali gerbil has an elongated snout and, as in the case of the taterillins, a laterally compressed brain skull. The back of the skull is wide, the bony ridges above the eye sockets are thick and the nasal bones extend far beyond the front teeth. In the top view, the parts of the wart are not noticeable. As in real mice, the posterior palatal holes are almost completely regressed. The palate is wider at the front than at the back, and the rows of teeth come closer together at the back. There are a couple of noticeable pits in the back of the palate.

The bony parts of the chewing apparatus are highly specialized. The zygomatic plate is similar to that of the actual gerbils . Your keel is not particularly elongated and rather low. The area of ​​origin of the lateral part of the masticatory muscle is enlarged mainly by the pronounced bulge of the zygomatic plate and the orbital shield is widened. The construction of the original surface of the temporal muscle is the most advanced of the gerbils. The temporal plate of the brain skull is very narrow and delimited at the top by a pronounced bone ridge. The complete absence of the muscle process on the ascending branch of the lower jaw is unique among the mice . In connection with the narrow temporal plate and the wide orbital shield, it is a derived peculiarity of the Somali gerbil. Due to the lack of the muscle process, the lower jaw is extremely weak. Apart from this peculiarity, however, it is typically trained for gerbils.

The timpani are also highly specialized, fully inflated, and large. As with the “typical reindeer mice” (Gerbillini) and unlike the taterillines, the proportions of the tympanic part and the wart part are equally developed. The distension of the wart part is quite complicated. Based on the structure and the position of the septum separating the essential atria of the wart part, it can be assumed that the wart part was initially inflated from the front and then from below. This results in the diagonal position of the partitions of the wart part, similar to that of the Cape short-tailed gerbil and the advanced Namib gerbil . The position of the small, posterior cell ( cellula mastoidea posterior ) of the mastoid process is similar to these . However, a slight additional inflation from below led to the formation of a small lower septum similar and possibly homologous to the septum ( septum mastoideum ventralis ) in the "typical gerbils".

denture

1 · 0 · 0 · 3  =  16
1 · 0 · 0 · 3
Tooth formula of the Somali gerbil

The Somali gerbil's teeth are one of the most specialized of the gerbils. The molars are higher crowned than those of the actual gerbil and are more similar in pattern to those of the racing rats . They have transverse ridges that run at an angle in the first molar, especially that of the lower jaw. The inclination is opposite to that of the brewer gerbil and the inner indentations are shifted backwards in relation to the outer ones. This secondary asymmetry of the molars is compensated for towards the rear by the approach of the upper rows of teeth to one another. The transverse ridges of the upper jaw teeth take a perpendicular position in relation to the longitudinal chewing movement of the lower rows of teeth.

In contrast to other recent gerbils, the first and second mandibular molars have, in addition to the actual cusps, two additional, independent, original cusps , the protoconulid and the hypoconolid. Although the anteroconid of the first mandibular molar is large, unlike in all other recent gerbils except for the brewer gerbil, it does not include the protoconulide, so that this remains independent even with worn teeth. It is very small and is occasionally missing due to individual variations or age-related changes. A well-developed hypoconulid occurs in the first and second mandibular molars and distinguishes the Somali gerbil from all other recent gerbils.

Karyotype

Karyotype
2n = 18 NF a = 34

According to Capanna and Merani (1981), the number of chromosomes is 18 and the arm number of autosomes is 34.

Way of life and behavior

Little is known about the way of life and behavior of the Somali gerbil. Historical records suggest that their population density is low. Their habitat are open, dry steppes of short grass and areas with isolated shrubs . It was found on sandy soils near wells and in sandy deserts . The weak lower jaw suggests a diet of soft foods, possibly fruits and soft insects . Despite the weak lower jaw, fights among conspecifics are known.

Spread and endangerment

The range of the Somali gerbil is Somalia and the east of Ethiopia . It was found in the Haud and Nugaal valleys and is known only from a few finds from the Holocene of Ethiopia and Somalia. However, it may be more widespread than previously known in this under-explored region.

The International Union for Conservation of Nature IUCN (2008) does not have sufficient data on the endangered status of the Somali gerbil. Up-to-date information on the extent of their occurrence, demands on the environment, threats and protection status is missing. Their habitat is threatened and destroyed by overgrazing by goats , sheep and cattle . However, the effect of this on the Somali gerbil is unclear and further research is needed. It is not known whether it can exist in disturbed or remodeled habitats. Protective measures do not exist and it is also unknown whether it occurs in protected areas. However, the population development of the Somali gerbil is stable. From 1996 to 2004 it was classified as endangered ( vulnerable ) because its habitat had decreased by 20 percent within a decade.

Systematics and nomenclature

Internal and external systematics

The Somali gerbil is the only species in the genus Ammodillus . There is no distinction between subspecies .

With regard to the peculiar bloating of the wart part, it shows the greatest similarity with the Cape short-tailed gerbil and the advanced Namib gerbil . The slight additional inflation from below, on the other hand, is similar and possibly homologous to that of the "higher gerbils" (Rhombomyina). The additional, independent secondary humps of the lower jaw teeth indicate a very early origin of the Somali gerbil. Due to the early separation from the other gerbils, it could have retained these original features of the mice's teeth that were lost in other recent gerbils. This can be a systematic classification on the same rank as the warrant of the other main groups of gerbils.

History of the system

Due to the characteristics of the dentition, John Reeves Ellerman suspected an isolated position of the Somali gerbil within the gerbil in 1941 and Francis Petter placed it in 1975 in his phylogenetic scheme along with some other genera at the base of the gerbil.

Igor Jakowlewitsch Pawlinow proposed a separate tribe for the Somali gerbil in 1981 and, due to the unique structure of the molars, introduced it in 1982 as the third subfamily Ammodillinae within the gerbil family, next to the taterillins and the "typical gerbils" (Gerbillinae):

 Gerbils (Gerbillidae)  

 Taterillins (Taterillinae)


   

 Somali gerbil (Ammodillinae)


   

 "Typical gerbils" (Gerbillinae)


Template: Klade / Maintenance / 3

In 1989 Hayan Tong also arranged them almost basally within the gerbils as a sister species of the "typical gerbils":

 Gerbils (Gerbillidae)  
  NN  

 Somali gerbil


   

 "Typical gerbils"



   

 Taterillins



Molecular genetic studies on the position of the Somali gerbil are still lacking (Pawlinow, 2008).

nomenclature

The type specimen of the Somali gerbil collected Charles Victor Alexander Peel in a process called "Gooder" or "Goodar" locality in British Somaliland . William Edward de Winton described it in March 1898 as Gerbillus imbellis , the type species of the genus Ammodillus described by Oldfield Thomas in August 1904 . The Latin epithet imbellis ('unwarlike, powerless') refers to the weak lower jaw. The generic name Ammodillus is made up of the Greek άμμος ( ammos 'sand') and Dipodillus . Igor Jakowlewitsch Pawlinow described the Ammodillini tribe in 1981. There are no synonyms.

Originally as Somali pygmy gerbil described bellows is assigned according to Thomas (1910) of the Somali gerbil. A Somali specimen consisting of an upper skull and lower jaw bears inventory numbers 4, 5, 9, 16 in the British Museum in London.

Somali gerbil and human

"Somali gerbil" (Grzimek, 1988; Wrobel, 2006) is used as a German common name . The Somali name is walo .

Web links

literature

Used literature:

  • Glover Morrill Allen: A checklist of African Mammals . In: Bulletin of the Museum of Comparative Zoology (Harvard College) . tape 83 , 1939, ISSN  0027-4100 , pp. 1-763 .
  • Gudrun Daxner-Höck: The vertebrate fauna from the Old Pliocene (Pont) from Eichkogel near Mödling (Lower Austria). IV. Gerbillinae (Rodentia, Mammalia) . In: Annals of the Natural History Museum in Vienna . tape 76 , 1972, ISSN  0083-6133 , pp. 143-160 .
  • Ralph Evelyn Drake-Brockman: The Mammals of Somaliland . Hurst and Blackett, London 1910.
  • John Reeves Ellerman: The Families and Genera of Living Rodents . Volume II. Family Muridae. British Museum (Natural History), London 1941.
  • Laurent Granjon, Duane A. Schlitter: Ammodillus imbellis . In: IUCN (Ed.): IUCN Red List of Threatened Species . 2008.
  • Systematic overview of mammals . In: Bernhard Grzimek (Ed.): Grzimeks Enzyklopädie Säugetiere . tape 11 , p. 11–55 (eleven-volume licensed edition of the original edition from 1988).
  • Jonathan Kingdon: The Kingdon Field Guide to African Mammals . A&C Black Publishers, London 2007, ISBN 978-0-7136-6513-0 (first edition: 1997, reprint of the original edition from 1997).
  • Malcolm C. McKenna, Susan K. Bell: Classification of Mammals Above the Species Level . Columbia University Press, New York 1997, ISBN 0-231-11012-X .
  • Guy G. Musser, Michael D. Carleton: Superfamily Muroidea . In: Don E. Wilson, DeeAnn M. Reeder (Eds.): Mammal Species of the World. A Taxonomic and Geographic Reference . 3. Edition. Johns Hopkins University Press, Baltimore 2005, ISBN 0-8018-8221-4 , pp. 894-1531 .
  • Ronald M. Nowak: Walker's Mammals of the World . 6th edition. Johns Hopkins University Press, Baltimore / London 1999, ISBN 0-8018-5789-9 .
  • Igor Jakowlewitsch Pawlinow: A review of phylogeny and classification of Gerbillinae (Mammalia: Rodentia) . In: Soologicheskie issledovanija . No. 9 , 2008, ISSN  1025-532X , p. 1-68 .
  • Ernest P. Walker: Mammals of the World . 3. Edition. Johns Hopkins University Press, Baltimore / London 1975, ISBN 0-8018-1657-2 .
  • Murray Wrobel (Ed.): Elsevier's Dictionary of Mammals . Elsevier, London 2006, ISBN 0-444-51877-0 .

Literature used indirectly:

  • Ernesto Capanna, María S. Merani: Karyotypes of Somalian rodent populations. 2. The chromosomes of Gerbillus dunni (Thomas, 1904), Gerbillus pusillus Peters, 1878 and Ammodillus imbellis (De Winton, 1898) (Cricetidae: Gerbillinae) . In: Monitors zoologico italiano. Supplemento . tape 15 , 1981, ISSN  0374-9444 , pp. 227-240 .
  • William Edward de Winton: Annales and Magazine of Natural History, Series 7 . tape 1 , 1898, p. 249 .
  • Ugo Funaioli: Guida breve dei mammiferi della Somalia . Instituto agronomico per l'oltremare (Biblioteca agraria tropicale), Florence 1971.
  • Igor Jakowlewitsch Pawlinow: [Systematic position of gerbills of the genus Ammodillus Thomas, 1904] . In: Soologitscheski schurnal . tape 60 , no. 3 , 1981, ISSN  0044-5134 , pp. 472–474 (Russian, with English summary).
  • Igor Jakowlewitsch Pawlinow: [Phylogeny and classification of the subfamily Gerbillinae] . In: Bjulleten Moskowskowo obschtschestwa ispytatelei prirody. Otdel biologically . tape 87 , no. 2 , 1982, ISSN  0027-1403 , pp. 19–31 (Russian, with an English summary).
  • Francis Petter: La diversite des Gerbillides . In: Monographiae Biologicae . tape 28 , 1975, ISSN  0077-0639 , pp. 177-183 .
  • Jean Roche, Francis Petter: Faits nouveaux concernant trois gerbillides mal connus de Somalie: Ammodillus imbellis (De Winton), Microdillus peeli (De Winton), Monodia juliani (Saint Leger) . In: Monitors Zoologico Italiano. Supplemento . tape 2 , 1968, ISSN  0374-9444 , p. 181-198 .
  • Oldfield Thomas: [Title unknown] . In: Annales and Magazine of Natural History, Series 7 . tape 14 , 1904, pp. 102 .
  • Oldfield Thomas: Further new African mammals . In: Annales and Magazine of Natural History, Series 8 . tape 5 , 1910, pp. 191-202 .
  • Haiyan Tong: Origine et évolution des Gerbillidae (Mammalia, Rodentia) en Afrique du Nord . In: Mémoires de la Société géologique de France, nouvelle série . tape 155 , 1989, ISBN 2-85363-050-1 , ISSN  0249-7549 , pp. 1-120 .
  • Derek Yalden, Malcolm Largen, D. Kock: Catalog of the mammals of Ethiopia. 2. Insectivora and Rodentia . In: Monitors zoologico italiano. Supplemento . tape 8 , 1976, ISSN  0374-9444 , pp. 1-118 .

Individual evidence

  1. ↑ a b c d e f Pawlinow, 2008 (pp. 40–41)
  2. ↑ a b c d e f g h Ellerman, 1941 ( pp. 524–525 )
  3. ↑ a b c d e f g Drake-Brockman, 1910 ( p. 124 )
  4. ↑ a b c Kingdon, 1997 (p. 196)
  5. ↑ a b c d e f g h Nowak, 1999 (pp. 1453–1454)
  6. ↑ Funaioli, 1971 → Quoted in: Nowak, 1999 (p. 1453)
  7. ↑ a b Pawlinow, 2008 (p. 41, Fig. 16)
  8. ↑ Pawlinow, 2008 (p. 41, Fig. 1d)
  9. ↑ Pawlinow, 2008 (p. 41, Fig. 2b)
  10. ↑ a b Pawlinow, 2008 (p. 11)
  11. ↑ Pawlinow, 2008 (p. 41, Fig. 4d)
  12. ↑ Pawlinow, 2008 (p. 41, Fig. 5c)
  13. ↑ Capanna and Merani, 1981 → Quoted from: bionet.nsc.ru
  14. ↑ a b c d Granjon and Schlitter, 2008 ( " Ammodillus imbellis " )
  15. ↑ Walker, 1975 (p. 856)
  16. ^ Roche and Petter, 1968 → Quoted in: Musser and Carleton, 2005 ( " Ammodillus imbellis " p. 1212)
  17. ↑ Yalden and co-workers, 1976 → Quoted in: Musser and Carleton, 2005 ( " Ammodillus imbellis " p. 1212)
  18. ↑ a b McKenna and Bell, 1997 (p. 160)
  19. ↑ a b Pawlinow, 2008 (p. 41).
  20. ↑ a b Musser and Carleton, 2005 ( " Ammodillus " p. 1212)
  21. ^ Pavlinow, 2008 (p. 19)
  22. ↑ Petter, 1975 → Quoted in: Pawlinow, 2008 (Fig. 10a)
  23. ↑ Pawlinow, 1981 → Quoted in: Musser and Carleton, 2005 ( " Ammodillus " p. 1212)
  24. ↑ Pawlinow, 1982 → Quoted in: Pawlinow, 2008 (pp. 31–32)
  25. ↑ Tong, 1989 → Quoted in: Pawlinow, 2008 (p. 29, p. 41, Fig. 10c)
  26. ↑ Pavlinow, 2008 (p. 29)
  27. ↑ de Winton, 1898 → Quoted in: Allen, 1939 ( p. 318 )
  28. ↑ Thomas, 1904 → Quoted in: Allen, 1939 ( p. 318 )
  29. ↑ Thomas, 1910 → Quoted in: Nowak, 1999 (p. 1448)
  30. ↑ Daxner-Höck, 1972 (p. 144, p. 152; PDF; 3.5 MB)
  31. ↑ Grzimek, 1988 (p. 37)
  32. ↑ Wrobel, 2006 ( p. 19 )