Leptictidium
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2008-07-02T16:46:56Z
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{{Taxobox
| name = ''Leptictidium''
| fossil_range = [[Eocene]]
| image = Leptictidium auderiense skeleton.JPG
| image_caption = ''Leptictidium auderiense'' skeleton at the [[Muséum national d'histoire naturelle]] ([[Paris]])
| image_width = 200px
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Mammal]]ia
| subclassis = [[Theria]]
| ordo = [[Leptictida]]
| familia = [[Pseudorhyncocyonidae]]
| genus = '''''Leptictidium'''''
| subdivision_ranks = [[Species]]
| subdivision =
*''[[Leptictidium auderiense|L. auderiense]]''
*''[[Leptictidium ginsburgi|L. ginsburgi]]''
*''[[Leptictidium nasutum|L. nasutum]]''
*''[[Leptictidium sigei|L. sigei]]''
*''[[Leptictidium tobieni|L. tobieni]]''
}}
'''''Leptictidium''''' ("graceful [[weasel]]" in [[Latin]]) is an [[extinction|extinct]] [[genus]] of small [[mammal]]s; together with [[macropod]]s and [[human]]s, they are the only known completely [[bipedal]] mammals. Comprising five species, they resembled today's [[elephant shrew]]s. They are especially interesting for their combination of characteristics typical of primitive [[eutheria]]ns with highly specialised adaptations, such as powerful hind legs and a long tail which aided in locomotion. They were omnivorous, their diet a combination of [[insect]]s, [[lizard]]s and small [[mammal]]s. One of the first branches to split from basal eutherians,<ref name="SL">{{cite journal | author = Adrian Lister, Gerhard Storch | date = [[July 22]], [[1985]]| title = ''Leptictidium nasutum'' n sp., ein Pseudorhyncocyonide aus dem Eozän der "Grube Messel" bei Darmstadt (Mammalia, Proteutheria) | journal = Senckenbergiana lethaea | volume = 66 | pages =| url =}}</ref> they appeared in the Lower [[Eocene]], a time of warm temperatures and high humidity, roughly fifty million years ago. Although they were widespread throughout [[Europe]], they became extinct around thirty-five million years ago with no descendants,<ref name=McK&B>{{cite book | author = McKenna, M. C, and S. K. Bell | year = 1997 | title = Classification of Mammals Above the Species Level | publisher = Columbia University Press | id = ISBN 023111012X}}</ref> probably due to the fact that they were adapted to live in [[forest]] [[ecosystem]]s and were unable to adapt to the open plains of the [[Oligocene]].
==Description==
[[Image:Elephant shrew.jpg|thumb|left|''Leptictidium'' resembled today's [[elephant shrew]]s.]]
''Leptictidium'' is a special animal because of the way its anatomy combines quite primitive elements with elements which prove a high degree of specialisation. It had small fore legs and large hind legs, especially at the distal side (that further from the body). The lateral [[phalanges of the hand|phalanges]] of its forelegs (fingers I and V) were very short and weak, finger III was longer and fingers II and IV were roughly equal in size, and slightly shorter than finger III. The tips of the phalanges were elongated and tapered.<ref name="SL"/>
The [[ankle]]s and the [[ilium (bone)|ilio]][[sacrum|sacral]] [[articulation (anatomy)|articulation]] were quite loosely fixed, while the [[pelvis]] had a flexible joint with only one [[coccygeal vertebra]]. The anteorbital [[muscle]] fenestrae in their crania suggest they probably had a long and mobile snout, similar to that of elephant shrews.
''Leptictidium'' had wide [[diastema (dentistry)|diastemata]] in the antemolar row,<ref name="WVK-GS">{{cite journal | author = Wighart von Koenigswald, Gerhard Storch | date = [[March 16]], [[1987]]| title = ''Leptictidium tobieni'' n sp., ein dritter Pseudorhyncocyonide (Proteutheria, Mammalia) aus dem Eozän von Messel | journal = Cour. Forsch.-Inst. Senckenberg | volume = 91 | pages = 107–116, 9 Abb.| url =}}</ref> its upper [[molar tooth|molar teeth]] were more transverse than those of the North American [[Leptictidae|leptictids]] and its fourth [[premolar]]s were molariform.<ref name="AgeofMammals">{{cite book | last = D. Rose | first = Kenneth | coauthors = Archibald, J. David | title = The Beginning of the Age of Mammals | url = http://books.google.com/books?id=3bs0D5ix4VAC&printsec=frontcover&dq=leptictidium&hl=es | accessdate = 20-01-2008 | year = 2006 | publisher = The Johns Hopkins University Press | location = | chapter = | chapterurl =}}</ref> Its C1 [[canine tooth|canines]] were incisiviform. Its [[dentition]] was quite small in comparison to the size of the [[mandible]] and the animal as a whole.<ref name="WVK-GS"/>
It varied between 60 and 90 [[centimetre|cm]] (24-36 [[inch|in]]) in length<ref>{{cite web | last = Chaisson | first = Eric J. | year = 2001 | url =http://www.bbc.co.uk/nature/wildfacts/factfiles/431.shtml | title = Leptictidium wildfacts | work = [http://www.bbc.co.uk/nature/animals/ Animal wildfacts] | publisher = BBC | accessdate = 30-12-2007}}</ref> (more than half of which belonged to the bald tail),<ref name="Paleocene mammals">{{cite web | last = Jehle | first = Martin | year = 2007 | url = http://www.paleocene-mammals.de/insectivores.htm | title = Insectivore-like mammals: Tiny teeth and their enigmatic owners | work = [http://www.paleocene-mammals.de/insectivores.htm Paleocene Mammals] | publisher = Martin Jehle | accessdate = 30-12-2007}}</ref> and 20 cm (8 in) in height. It weighed a couple of kilograms.<ref name="Kenozoicum"/> These sizes could [[Leptictidium#Comparison of the Messel species|vary from one specimen to another]].
===Locomotion===
One of the mysteries about ''Leptictidium'' is whether it moved by running or by jumping. Because there are very few completely [[bipedal]] mammals, it is difficult to find an appropriate living model to compare it with. If the [[kangaroo]] are used, it is probable that ''Leptictidium'' ran with its body tilted forward, using its tail as a counterweight.<ref name="Kenozoicum">{{cite web | last = | first = Kenozoicum | year = 2007 | url = http://www.kenozoicum.nl/database/leptictidium.html | title = Leptictidium | work = [http://www.kenozoicum.nl/database/leptictidium.html Leptictidium bij Kenozoicum.nl] | publisher = Kenozoicum.nl | accessdate = 30-12-2007}}</ref> On the other hand, [[elephant shrew]]s combine both types of [[animal locomotion|locomotion]]; they usually move [[quadruped|on four legs]], but they can run on two legs to flee from a predator.<ref name="Paleocene mammals">{{cite web | last = Jehle | first = Martin | year = 2007 | url = http://www.paleocene-mammals.de/insectivores.htm | title = Insectivore-like mammals: Tiny teeth and their enigmatic owners | work = [http://www.paleocene-mammals.de/insectivores.htm Paleocene Mammals] | publisher = Martin Jehle | accessdate = 30-12-2007}}</ref> Studies of the bone structure of ''Leptictidium'' have yielded contradicting information: its leg [[articulation (anatomy)|articulations]] appear too weak to have supported the shock of repeated jumps, but its long feet were obviously not adapted for jumping rather than running.
Kenneth D. Rose compared the species ''L. nasutum'' with the [[leptictidae|leptictid]] ''[[Leptictis|Leptictis dakotensis]]''. ''L. dakotensis'' had a series of traits which show it was a running animal which sometimes moved by jumping. Despite the marked similarities between ''Leptictis'' and ''Leptictidium'', there are certain differences in their skeletons which prevent the example of ''Leptictis'' from being used to determine with certainty the way ''Leptictidium'' moved: the most important being that, unlike ''Leptictis'', the [[tibia]] and the [[fibula]] of ''Leptictidium'' were not fused together.<ref name="Rose">{{cite journal | last = Rose | first = Kenneth D. | coauthors = | date =| title = The postcranial skeleton of early Oligocene ''Leptictis'' (Mammalia: Leptictida), with preliminary comparison to ''Leptictidium'' from the middle Eocene of Messel | journal = | volume = | pages =| url = }}</ref>
While some [[paleontology|paleontologists]] argue that ''Leptictidium'' was obviously a running animal, others reply that what is obvious is that it was saltatorial. The fact is that the way this [[eutheria]]n moved remains a controverted subject.
==Behaviour==
''Leptictidium'' was probably a [[diurnal]] animal which went out to hunt twice a day, once in the morning and once in the afternoon. One of the first things it did after waking up was [[grooming]] intensively. It is believed that it showed a particular habit when it hunted; it cleared paths in the [[jungle]] where it lived. Every morning and every afternoon it kept itself busy patrolling these paths, catching any prey it found and clearing them from any object which hindered the way. Keeping these paths clear was of utter importance, as they were the way it used to flee if ever a predator attacked it.<ref name="Haines2001">{{cite book | last = Haines | first = Tim | coauthors = | title = Walking with Beasts | url = http://www.amazon.com/WALKING-BEASTS-TIM-HAINES/dp/0563537639/ref=sr_1_2?ie=UTF8&s=books&qid=1199057543&sr=1-2 | accessdate = 30-12-2007 | year = 2001 | publisher = BBC Books | location = Londres | chapter = New Dawn | chapterurl =}}</ref>
Since ''Leptictidium'' young were very vulnerable to attacks of predators, it is probable that they were born quite developed and that they became independent when they were still quite young. From the behaviour of today's elephant shrew, the possibility can be suggested that ''Leptictidium'' young went out to hunt with their mother, and that they learned to distinguish prey by licking their mother's mouth when she had just caught an animal, in order to know the flavour of food.<ref>{{cite web | last = | first = BBC | year = 2001 | url = http://www.abc.net.au/beasts/evidence/prog1/page5_2.htm | title = Leptictidium | work = [http://www.abc.net.au/beasts/evidence/prog1/page5_2.htm WWB Evidence] | publisher = ABC | accessdate = 20-01-2008}}</ref>
Perfectly preserved [[fossil]]s of three different species of ''Leptictidium'' have been found in the [[Messel pit]] in [[Germany]]. The marks on their fur have been preserved, as well as their [[stomach]] contents, which reveal ''Leptictidium'' were [[omnivore]]s which fed on [[insect]]s, [[lizard]]s and small [[mammal]]s.<ref name="Haines2001"/> The [[holotype]] of ''L. tobieni'' also had pieces of [[leaf|leaves]] and notable amounts of sand in its abdomen, but it cannot be determined with certainty if the animal swallowed it.<ref name="WVK-GS"/>
==Habitat==
[[Image:Jaciments de Messel.jpg|thumb|right|Excavations at the Messel pit.]]
{{main|Eocene}}
{{main|Messel pit}}
''Leptictidium'' lived in the [[Europe]]an [[subtropical]] [[forest]]s of the [[Eocene]]. From the beginning of this period, the temperature of the planet rose in one of the quickest (in [[geology|geological]] terms) and most extreme episodes of global warming in the geological record, termed [[Paleocene–Eocene Thermal Maximum|Palaeocene–Eocene Thermal Maximum]]. It was an episode of quick and intense (of up to 7°C in high latitudes) warming which lasted less than 100,000 years.<ref>http://pubs.giss.nasa.gov/docs/2003/2003_Schmidt_Shindell.pdf</ref> The Thermal Maximum caused a great extinction which is used to distinguish the Eocene [[fauna]] from that of the [[Paleocene|Palaeocene]].
The global climate of the Eocene was probably the most homogeneous of the [[Cenozoic]]; the [[temperature gradient]] from the [[equator]] to the [[geographical pole|poles]] was half that of today's, and the deep [[ocean current]]s were exceptionally warm. The polar regions were much warmer than today, maybe as warm as the [[Pacific Northwest]] nowadays. Temperate forests reached the poles themselves, while rainy tropical climates reached 45º N. The greatest difference was in temperate latitudes; nevertheless, the climate at the [[tropic]]s was probably similar to today's.<ref name="Stanley">{{cite book | last = Stanley | first = Steven M. | coauthors = | title = Earth System History | url = http://en.wikipedia.org/wiki/Special:BookSources/0716728826 | year = 1999 | publisher = W.H. Freeman and Company| Data d'accés: 05-04-2008 | location = New York | chapter =}}</ref>
In the Eocene, most of what today is [[Europe]], the [[Mediterranean sea|Mediterranean]] and south-west [[Asia]] was submerged under the [[Tethys Sea]]. Both [[continent]]s were separated by the [[Turgai Strait]] (an [[epeiric sea]]).<ref name="Scotese">{{cite web | last = Scotese | first = Christopher | year = 2002 | url = http://www.scotese.com/newpage9.htm | title = Paleomap project | work = [http://www.scotese.com ''Paleomap project''] | publisher = Christopher Scotese | accessdate = 23-01-2008}}</ref> Thanks to high humidity and temperatures, most of the European continent was covered in [[vegetation]].
[[Image:Lake nyos.jpg|thumb|left|The Messel pit zone included a [[volcanic lake]] satured with reactive gases, similar to [[Cameroon]]'s [[Lake Nyos]].]]
The region which today is [[Germany]] was in a [[volcano|volcanically]] active zone during the Eocene. It is thought that the [[Messel pit]] could have been the old location of a volcanic lake saturated with [[carbon dioxide|CO<sub>2</sub>]]. The lake would periodically release the gas it contained, creating a lethal cloud which would asphyxiate any animal in its path. This would explain the great number of non-aquatic species which have been found in the old lake-bed of the Messel pit.
In the lush forests of this region, ''Leptictidium'' shared its habitat with animals such as ''[[Godinotia]]'', ''[[Pholidocercus]]'', ''[[Palaeotis]]'' or ''[[Propalaeotherium]]''. There were also predators: ''[[Asiatosuchus]]'', ''[[Lesmesodon]]'' or the [[Formicium|Messel giant ant]]. The alpha predator was ''[[Gastornis]]'', a carnivorous bird almost two metres tall.
==Species==
[[Image:Leptictidium auderiense Tobien 1962.JPG|thumb|right|Photograph of the [[Muséum national d'histoire naturelle|MNHN]]'s ''Leptictidium auderiense'', with a full view of the long tail.]]
The genus ''Leptictidium'' includes five [[specie]]s:
===''Leptictidium auderiense''===
{{main|Leptictidium auderiense}}
Described by [[Heinz Tobien]] in 1962 based on a series of [[lower jaw]]s from the [[Lutetian]] faunal stage. Tobien also uncovered a small skeleton he defined as a [[paratype]] of the species, but Storch and Lister proved in 1985 that, in fact, the skeleton did not even belong to the [[genus]] ''Leptictidium''.<ref name="WVK-GS"/> It was the smallest species of all and was only sixty centimetres long. Several skeletons have been found at the Messel pit.<ref name="Messel">{{cite journal | last = | first = | coauthors = Michael Morlo, Stephan Schaal, Gerald Mayr & Christina Seiffert | date = [[December 9]], [[2004]]| title = An annotated taxonomic list of the Middle Eocene (MP 11) | journal = Cour. Forsch.-Inst. Senckenberg | volume = | pages =| url = http://www.senckenberg.de/files/content/forschung/abteilung/terrzool/ornithologie/morlo_et_al.pdf}}</ref> [[Christian Mathis|Mathis]] remarks the exceptional development of the paraconid (or mesiobucal cusp) of the lower P4 [[premolar]].<ref name="Mathis">{{cite journal | last = Mathis | first = C. | coauthors = | date = [[1989]]| title = Quelques insectivores primitifs nouveaux de l'Eocène supérieur du sud de la France | journal = Bulletin du Muséum national d'histoire naturelle de Paris | volume = 11 | pages = 33–64| url = }}</ref> Its premolars and [[molar tooth|molars]] were quite small in comparison to the dentition as a whole. The name of the species refers to the [[Roman Empire|Roman]] settlement of [[Dieburg|Auderia]].
===''Leptictidium ginsburgi''===
{{main|Leptictidium ginsburgi}}
Described by [[Christian Mathis]] in 1989. Fossils have been found in the lagerstätte at Robiac, Le Bretou, Lavergne, La Bouffie, Les Clapiès, Malpérié and Perrière ([[France]]), in [[Ludian|Upper Ludian]] strata. The mesostyle typical of the ''Leptictidium'' genus is not developed in this species.<ref name="Mathis"/> The species is dedicated to [[Léonard Ginsburg]], [[France|French]] [[paleontologist]] and deputy director of the [[Muséum national d'histoire naturelle]] in [[París]].
===''Leptictidium nasutum''===
{{main|Leptictidium nasutum}}
Described by [[Adrian Lister]] and [[Gerhard Storch]] in 1985. It was a middle-sized species which was seventy-five centimetres long. Several skeletons have been found in the Messel pit,<ref name="Messel"/> in [[Lutetian|Lower Lutetian]] strata. The tail of this species had 42-43 [[vertebra]]e,<ref name="SL"/> a number surpassed among [[mammal]]s solely by the [[Long-tailed Pangolin]]. Its [[premolar]] and [[molar tooth|molar]] teeth were quite small in comparison to the dentition as a whole. The name of the species refers to the [[nose]] of the animal. The [[holotype]] is the complete skeleton of an adult specimen kept in the [[Forschungsinstitut Senckenberg]] in [[Frankfurt am Main]].<ref name="SL"/>
===''Leptictidium sigei''===
{{main|Leptictidium sigei}}
Described by [[Christian Mathis]] in 1989. Fossils have been found in the lagerstätte at Sainte-Néboule, Baby, Sindou and Pécarel ([[France]]), and it has a more primitive appearance than ''L. nasutum''. It is known mainly from isolated teeth. It has a P4 with a much reduced paraconid, as well as very distinct entoconids and hypoconulids on M1 and M2.<ref name="Mathis"/> The species is dedicated to [[Bernard Sigé]], [[France|French]] [[paleontologist]].
===''Leptictidium tobieni''===
{{main|Leptictidium tobieni}}
[[Image:Leptictidium tobieni.jpg|thumb|right|Fossil of ''Leptictidium tobieni'' at the <br/>[[Hessisches Landesmuseum Darmstadt]].]]
Described by [[Wighart von Koenigswald]] and [[Gerhard Storch]] in 1987. It was the largest species of all at ninety centimetres long. It is one of the species found in the Messel pit,<ref name="Messel"/> in [[Lutetian]] strata. The species is dedicated to [[Heinz Tobien]], descriptor of the genus ''Leptictidium'' and promotor of research in the Messel pit during the 1960s. The [[holotype]] is a complete and perfectly preserved skeleton of an adult specimen which was uncovered in September 1984 and which can be found at the Hessisches Landesmuseum Darmstadt.<ref name="WVK-GS"/> There is also a paratype; a non-complete and badly preserved specimen which can be found at the Institut Royal des Sciences Naturelles de Belgique.
It has a relatively robust [[mandible]] with a relatively large mesostyle. The molariform premolar teeth are a characteristic of the ''Leptictidium'' genus as a whole which is very marked in the P4 premolars of ''L. tobieni''. The well-developed mesostyle and the transversal configuration of the upper molars are other typical traits of this species.<ref name="WVK-GS"/>
===Comparison of the Messel species===
By observing the clear morphological differences in the dentition of the three species found in Messel, the possibility can be discarded that either the discovered [[fossil]]s are specimens of the same species but of different age, or that two of these forms belonged to the same species with a marked [[sexual dimorphism]].<ref name="WVK-GS"/>
The Messel species developed very quicly a series of characteristical evolutionary traits, common to all of them, which separe them from the lagerstätte of [[Quercy]].<ref name="Mathis"/>
This table compares the size of different specimens of each species found in the Messel pit <small>(sizes in millimetres)</small>.
{| class="wikitable"
!colspan="8"|Messel species comparison<ref name="WVK-GS"/>
|-
!colspan="1"| <small>species</small>
!colspan="2"|''L. auderiense''
!colspan="3"|''L. nasutum''
!colspan="2"|''L. tobieni''
|-
!colspan="1"|<small>specimens</small>
!colspan="1"|LNK Me <br/>418a
!colspan="1"|SMF <br/>78/1
!colspan="1"|SMF ME <br/>1143
!colspan="1"|LNK Me <br/>576
!colspan="1"|HLMD Me <br/>8059
!colspan="1"|HLMD Me <br/>8011a
!colspan="1"|I. R. Sc. N. B. <br/>M1475
|-
!colspan="1"|[[Cranium]]
|align="center"|67.4
|align="center"|67.2
|align="center"|88.2
|align="center"|89.8
|align="center"|88.6
|align="center"|101.1
|align="center"| -
|-
!colspan="1"|[[Head]]+[[torso]]
|align="center"|220
|align="center"|215
|align="center"|300
|align="center"|295
|align="center"|328
|align="center"|375
|align="center"| -
|-
!colspan="1"|[[Tail]]
|align="center"|(340)
|align="center"|375
|align="center"|450
|align="center"|445
|align="center"|454
|align="center"|500
|align="center"| -
|-
!colspan="1"|[[Humerus]]
|align="center"|31.8
|align="center"|32.3
|align="center"|41.9
|align="center"|41.9
|align="center"|43.1
|align="center"|45.7
|align="center"|46.6
|-
!colspan="1"|[[Ulna]]
|align="center"|29.4
|align="center"|31.8
|align="center"|45.6
|align="center"|44.2
|align="center"|45.3
|align="center"|51.2
|align="center"| -
|-
!colspan="1"|[[Radius (bone)|Radius]]
|align="center"|21.5
|align="center"|23.9
|align="center"|31.7
|align="center"|31.1
|align="center"|33.2
|align="center"|37.0
|align="center"|36.2
|-
!colspan="1"|[[Pelvis]]
|align="center"|54.5
|align="center"|56.5
|align="center"|77.8
|align="center"|77.1
|align="center"| -
|align="center"|85.7
|align="center"|(82)
|-
!colspan="1"|[[Femur]]
|align="center"|54.2
|align="center"|57.5
|align="center"|75.3
|align="center"|71.5
|align="center"|75.1
|align="center"|84.8
|align="center"|(82)
|-
!colspan="1"|[[Tibia]]
|align="center"|64.4
|align="center"|66.3
|align="center"|79.7
|align="center"|79.0
|align="center"|80.1
|align="center"|91.6
|align="center"|90.5
|-
!colspan="1"|[[Fibula]]
|align="center"|57.4
|align="center"|58.7
|align="center"|75.2
|align="center"|72.3
|align="center"| -
|align="center"|86.6
|align="center"| -
|-
!colspan="1"|[[Calcaneus]]
|align="center"|22.3
|align="center"|22.6
|align="center"|25.3
|align="center"|25.2
|align="center"| -
|align="center"|26.7
|align="center"|25.4
|-
!colspan="1"|[[Neurocranium]] †
|align="center"|33.0
|align="center"|31.6
|align="center"|38.7
|align="center"|39.3
|align="center"|37.5
|align="center"|42.2
|align="center"|42.5
|-
!colspan="1"|Height of the [[lower jaw|lower]] <br/>[[lower jaw|jaw]] below [[molar tooth|M2]]
|align="center"|5.7
|align="center"|5.6
|align="center"|6.9
|align="center"|6.6
|align="center"|6.4
|align="center"|9.0
|align="center"|9.5
|-
!colspan="1"|Height of the <br/>[[lower jaw|mandibular ramus]] ††
|align="center"|14.3
|align="center"| -
|align="center"|20.8
|align="center"|23.3
|align="center"|23.0
|align="center"|29.2
|align="center"|28.5
|-
|}
† <small>From the front edge of the orbit.</small><br/>
†† <small>Above the ''incisura praeangularis''.</small>
==Evolutionary tendencies==
In his work ''Quelques insectivores primitifs nouveaux de l'Eocène supérieur du sud de la France'' (1989), [[France|French]] [[paleontologist]] [[Christian Mathis]] studied the evolutionary tendencies of the genus ''Leptictidium'', based on the comparison of the most primitive and the most recent species. From this observations, Mathis remarks:<ref name="Mathis"/>
*an increase in size;
*a precocious merging of the hypoconulid and the entoconid on M3;
*a slight reduction of the width of the talonid on M3 in comparison to the anterior molars;
*the formation and development of a mesostile on the molariform jugal teeth P4-M3;
*the reduction of the parametastylar and metastylar regions of these same teeth (with some exceptions), in particular with a reduction of the parastylar lobe which rises less in the anterior part of M3 and possibly P4;
*a transverse shortening of the upper molarised teeth, which become more square;
*the development of accessory conuli on the preprotocrista and postprotocrista;
*the development of the postcingulum.
==Related species==
[[Image:TN Gill.jpg|thumb|right|[[Theodore Gill]] described the family Leptictidae in [[1872]].]]
Together with the [[genus]] ''[[Pseudorhyncocyon]]'', the five ''Leptictidium'' species form the family [[Pseudorhyncocyonidae]], one of the three which form the order [[Leptictida]]. These families and genera are:<ref>{{cite web | last = Haaramo | first = Mikko| year = 2007 | url = http://www.fmnh.helsinki.fi/users/haaramo/ | title = Mikko's Phylogeny Archive | work = [http://www.fmnh.helsinki.fi/users/haaramo/ Mikko's Phylogeny Archive] | publisher = Mikko Haaramo | accessdate = 30-12-2007}}</ref>
'''Order Leptictida'''
*Family [[Gypsonictopidae]] <small>(Van Valen, 1967)</small>
**Genus ''[[Gypsonictops]]'' <small>(Simpson, 1924)</small>
*Family [[Leptictidae]] <small>(Gill, 1872)</small>
**Genus ''[[Leptictis]]'' <small>(Leidy, 1868)</small>
**Genus ''[[Myrmecoboides]]'' <small>(Gidley, 1915)</small>
**Genus ''[[Ongghonia]]'' <small>(Kellner & McKenna, 1996)</small>
**Genus ''[[Palaeictops]]'' <small>(Matthew, 1899)</small>
**Genus ''[[Prodiacodon]]'' <small>(Matthew, 1929)</small>
**Genus ''[[Xenacodon]]'' <small>(Matthew & Granger, 1921)</small>
*Family [[Pseudorhyncocyonidae]] <small>(Sigé, 1974)</small>
**Genus '''''Leptictidium''''' <small>(Tobien, 1962)</small>
**Genus ''[[Pseudorhyncocyon]]'' <small>(Filhol, 1892)</small>
<small>Because Leptictida is a [[paraphyletic]] group, this list does not take into account the families or genera with an uncertain or disputed affiliation.</small>
==In documentaries==
[[Image:Leptictidium.jpg|left|thumb|On ''Walking with Beasts''.]]
A female ''Leptictidium'' and its young are the main characters in the first episode of the [[BBC]]'s [[paleontology]] series ''[[Walking with Beasts]]''. The episode narrates one day in the life of this animal of the Eocene.
The female ''Leptictidium'' appears for the first time after the fall of a [[micrometeorite]], when she meets another specimen of the same species just before [[dawn]]. She is forced to flee from a ''[[Gastornis]]'', hiding in the nest it has built at the base of a [[fig tree]]. Once the sun has risen, the mother goes out to hunt, looking for insects and [[cold-blooded]] animals which have not warmed up yet, and she hunts a [[frog]]. She reaches the shore of a lake, but she does not approach because an ''[[Ambulocetus]]'' has arrived from the coast. By midday she is forced to return to her nest despite the little success she has had, since it is the time there are more predators in the forest, and she sleeps until the afternoon.
When the hottest hours are over, the female goes out to hunt again. She uses her hindlegs to prepare the paths she will use to escape if a predator pursues her. This time, the young accompany the mother in her hunt. They are able to escape from the attack of a ''Gastornis'', which ends up killing a ''[[Propalaeotherium]]''. This time, they are successful and are able to feed well.
At nightfall, the ''Leptictidium'' are some of the few animals which are saved from a cloud of toxic gas, freed by the volcanic lake, thanks to the fact that their nest lay away from the path of the cloud. Instead, the ''Ambulocetus'' which had attacked them during the day dies asphyxiated by the [[carbon dioxide]], and the following morning the ''Leptictidium'' pass next to it, knowing it is dead.<ref>{{cite web | last = BBC | first = | year = 2002 | url = http://www.abc.net.au/beasts/ | title = Walking with Beasts | work = [http://www.abc.net.au/beasts/ ''Walking with Beasts'' on the ABC's website] | publisher = ABC | accessdate = 30-12-2007}}</ref>
==Bibliography==
===In English===
<div style="font-size:95%;">
* {{cite book
| author = Benton, M.
| title = Vertebrate Palaeontology
| year = 2000
| publisher = Oxford: Blackwell Publishers
| id = ISBN 0632056142
}}
* {{cite book
| author = Frey, E.; Herkner, B.; Schrenk, F.; Seiffert, C;
| title = Reconstructing organismic constructions and the problem of Leptictidium's locomotion
| year = 1993
| publisher = Darmstadt: Kaupia Darmstädter Beiträge zur Naturgeschichte
| id =
}}
* {{cite book
| author = Rose, K.
| title = The Beginning of the Age of Mammals
| year = 2006
| publisher = The Johns Hopkins University Press
| id = ISBN 0801884721
}}
</div>
===In French===
<div style="font-size:95%;">
* {{cite book
| author = Mathis, C.
| title = Quelques insectivores primitifs nouveaux de l'Eocène supérieur du sud de la France
| year = 1989
| publisher = Paris: Bulletin du Muséum national d'histoire naturelle
| id =
}}
</div>
===In German===
<div style="font-size:95%;">
* {{cite book
| author = Christian, A.
| title = Zur Biomechanik der Fortbewegung von Leptictidium (Mammalia, Proteutheria)
| year = 1999
| publisher = Frankfurt am Main: Courier Forschungsinstitut Senckenberg
| id =
}}
* {{cite book
| author = Maier, W.; Richter, G.; Storch, G.
| title = ''Leptictidium nasutum'' - ein archaisches Säugetier aus Messel mit außergewöhnlichen biologischen Anpassungen
| year = 1986
| publisher = Frankfurt am Main: Natur und Museum
| id =
}}
* {{cite book
| author = Storch, G.
| title = ''Leptictidium'' - ein archaischer Säuger
| year = 1987
| publisher = Naturwissenschaftliche Rundschau
| id =
}}
* {{cite book
| author = Storch, G.; Lister, A.
| title = ''Leptictidium nasutum'' - ein Pseudorhyncocyonide aus dem Eozän der Grube Messel bei Darmstadt (Mammalia, Proteutheria)
| year = 1985
| publisher = Frankfurt del Main: Senckenbergiana lethaea
| id =
}}
* {{cite book
| author = Tobien, H.
| title = Insectivoren (Mammalia) aus dem Mitteleozän (Lutetium) von Messel bei Darmstadt
| year = 1962
| publisher = Wiesbaden: Notizbl. hess. Landesamt. Bodenforsch.
| id =
}}
* {{cite book
| author = von Koenigswald; W.; Storch, G.
| title = ''Leptictidium tobieni'' n sp., ein dritter Pseudorhyncocyonide (Proteutheria, Mammalia) aus dem Eozän von Messel
| year = 1987
| publisher = Frankfurt del Main: Courier Forschungsinstitut Senckenberg
| id =
}}
* {{cite book
| author = von Koenigswald, W.; Wuttke, M.
| title = Zur Taphonomie eines unvollständigen Skelettes von ''Leptictidium nasutum'' aus dem Ölschiefer von Messel
| year = 1987
| publisher = Wiesbaden: Geol. Jb. Hessen
| id =
}}
</div>
==References==
{{reflist}}
==External links==
*[http://www.bbc.co.uk/nature/wildfacts/factfiles/431.shtml ''Leptictidium'' at BBC Science & Nature]
*[http://www.kenozoicum.nl/database/leptictidium.html ''Leptictidium'' at Kenozoicum.nl] {{nl}}
*[http://www.abc.net.au/beasts/ ''Walking with Beasts'' – Australian Broadcasting Corporation]
[[Category:Leptictids]]
[[Category:Eocene mammals]]
[[Category:Prehistoric mammals of Europe]]
[[Category:Eocene extinctions]]
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