Phylogeny and Evolution of the Gorgonopsia with a special reference to the skull and skeleton of GPIT-RE-7113 ('Aelurognathus?' parringtoni) [Elektronische Ressource] / vorgelegt vonEva V. I. Gebauer

Informations

• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2007
• Nombre de lectures: 39
• Langue: English
• Poids de l'ouvrage: 22 Mo

Extrait

Phylogeny and evolution of the
gorgonoPsia
with a sPecial reference to the
skull and skeleton of gPit/re/7113
(‘AelurognAthus?’ pArringtoni)
Dissertation
zur Erlangung des Grades eines Doktors der Naturwissenschaften
der Geowissenschaftlichen Fakultät
der Eberhard-Karls Universität Tübingen
vorgelegt von
Eva V. I. Gebauer
aus Würzburg
2007Tag der mündlichen Prüfung: 20.7. 2007
Dekan: Prof. Dr. Peter Grathwohl
1. Berichterstatter: Prof. Dr. W.-E. Reif
2. Berichterstatter: Prof. Dr. F. WestphalFür meine Eltern
„Suchen heißt: ein Ziel haben.
Finden aber heißt: frei sein, offen sein, kein Ziel haben.“
Hermann Hesse, SiddharthaPhylogeny and evolution of the gorgonoPsia ix
Table of ConTenTs
absTraCT i
Zusammenfassung iii
1 IntroductIon 1
1.1 Prelude 1
1.2 The history of gorgonopsian investigation 3
1.3 Gorgonopsian occurrence 5
1.3.1 The Karoo-Basin 5
1.3.2 East Africa 7
1.3.3 Russia 9
1.4 Outline and aim of this study 10
1.5 Material & methods 12
2 Part I: SyStematIcS and Phylogeny 15
2.1 The systematic position of GPIT/RE/7113 15
2.1.1 Introduction 15
2.1.2 Comparative re-description of GPIT/RE/7113 16
2.1.2.1 General remarks 16
2.1.2.2 Dentition 17
2.1.2.3 Skull 18
2.1.2.4 Lower jaw 27
2.1.2.5 Postcranial skeleton 32
2.1.3 Comparison of postcranial material of GPIT/RE/7113 with other taxa 46
2.1.4 History of GPIT/RE/7113 and discussion of literature 48
2.1.5 Comparison with Aelurognathus HaugHTon, 1924 50
2.1.6 Comparison with Sauroctonus progressus HarTmann-Weinberg, 1938 51
2.1.7 Conclusion 55x table of Contents
2.2 Re-assessment of the Gorgonopsia 57
2.2.1 Introduction 57
2.2.2 The genera from the Tapinocephalus Zone 58
2.2.3 The small sized genera and the possible existence of different ontogenetic states 62
2.2.3.1 Introduction 62
2.2.3.2 Cerdorhinus Broom, 1936 69
2.2.3.3 Paragalerhinus Sigogneau, 1970 71
2.2.3.4 Aloposaurus Broom, 1910 73
2.2.3.5 Cyonosaurus olSon, 1937 83
2.2.3.6 Aelurosaurus owen, 1881 93
2.2.3.7 Scylacognathus Broom, 1913 and Arctops watSon, 1914 107
2.2.4 Gorgonops oWen, 1876 and Scylacops broom, 1913 121
2.2.5 Arctognathus broom, 1911 and the new genus Njalila 139
2.2.6 Lycaenops broom, 1925 , Aelurognathus HaugHTon, 1924 and Prorubidgea broom, 156
1940
2.2.7 Sycosaurus HaugHTon, 1924, Leontocephalus broom, 1940 and Ruhuhucerberus 188
maisCH, 2002
2.2.8 Clelandina broom, 1948 and Broomicephalus brink & kiTCHing, 1953 206
2.2.9 Dinogorgon broom, 1936 and Rubidgea broom, 1938 213
2.2.10 Conclusion on the East African specimens 223
2.3 The in-group phylogeny of the Gorgonopsia 227
2.3.1 The classification of the Gorgonopsia sensu sigogneau-russell, 1989 and 227
ivakHnenko, 2002
2.3.2 Character discussion and data matrix 228
2.3.3 Discussion of the Cladogram and conclusions 243
3 Part II: FunctIonal analySeS 247
3.1 Introduction 247
3.2 Jaw mechanics in GPIT/RE/7113 247
3.2.1 Musculature 247
3.2.2 Jaw articulation 255
3.2.4 Conclusions 257Phylogeny and evolution of the gorgonoPsia xi
3.3 Limb movement in GPIT/RE/7113 259
3.3.1 Introduction 259
3.3.2 Shoulder joint 260
3.3.3 Forelimb 263
3.3.4 Hindlimb 264
3.4 Comparison with Smilodon fatalis 270
3.4.1 Introduction 270
3.4.2 Skull 272
3.4.3 Postcranial skeleton 285
3.4.3.1 Shoulder girdle 285
3.4.3.2 Forelimb 286
3.4.3.3 Vertebrae 291
3.4.3.4 Pelvic girdle 296
3.4.3.5 Hindlimb 297
3.4.4 Conclusions 299
referenCes 301
abbreviaTions used in figures 309
aCknoWledgemenTs 313
akademisCHer bildungsgang 315xii table of ContentsPhylogeny and evolution of the gorgonoPsia i
abStract
The Gorgonopsia, a group of carnivorous therapsids from the Upper Permian, is revised. The basis for this
re-assessment is the gorgonopsian material from the nowaCk-Collection, which is housed at the Geologisch-
Paläontologisches Institut Tübingen. The collection was founded by von huene and consists of finds from the
Ruhuhu- Valley in Tanzania that were discovered by nowaCk in the 1930s. It includes eight well-preserved
gorgonopsian specimens and nine incomplete and eroded skulls, which do not show the diagnostic characters
well enough to determine their taxonomic position. One of the best preserved specimens is an almost complete
skeleton, GPIT/RE/7113. It was allocated to the genus ‘Scymnognathus’ by von huene (1950) but was later
assigned to the taxon Aelurognathus? parringtoni by sigogneau (1970). A renewed investigation of the skull
revealed that the specimen could not be allocated to any South or East African taxon, but rather to the Russian
genus Sauroctonus. Thus, a true connection between the African and Russian biozones is established for the
first time.
The alpha-level taxonomy of the other specimens in the nowaCk-Collection is resolved as a result of a re-
assessment of the complete Gorgonopsia. This reassessment made it possible to carry out phylogenetic analyses,
and present the first computer-based cladogram of the Gorgonopsia. It is shown that the family Gorgonopsidae
does not include the genera Aloposaurus, Cyonosaurus and Aelurosaurus. Instead these taxa form the stem-
group representatives of the remaining taxa. Within the Gorgonopsidae only the subfamily Rubidgeinae could
be recognised whereas the other taxa constitute a gradual evolutionary pattern.
The second part deals with functional aspects of the Gorgonopsia, focusing on jaw mechanics and limb
movements. Here GPIT/RE/7113 was used again as a basis for comparative research because its well-preserved
postcranial skeleton enabled a thorough and detailed anatomical investigation
It is proposed that gorgonopsians were not only able to move in a dual gait fashion with the hindlimbs, as stated
by kemP (1982), but also with their forelimbs. The shape of the humeral head and the glenoid, which allow for
a variety of positions, provide morphologic evidence for this hypothesis. In addition it is postulated that the
animal was able to move faster when the humerus was placed at a sloping angle, because the humeral rotation
would be more extensive, which in turn would increase the stride length.
The main interest, however, was the possibility that the enlarged canines of gorgonopsians and saber tooth cats
might portend to further similarities in their skulls and postcranial skeletons. In order to investigate this idea,
specimen GPIT/RE/7113 was closely compared with a specimen of Smilodon fatalis. In addition, both GPIT/
RE/7113 and Smilodon fatalis were with their closest relatives, therocephalians and cynodonts, and
Panthera leo, respectively. It is shown that the skull morphology is highly modified to be able to accommodate
the high root of the caninus, that the incisivi are arranged in a parabolic arch to serve as an additional gripping
device, and that a specialised jaw mechanism allows for a wide gape. In the postcranial skeleton, the massive
humeri display well-developed muscle attachment areas and the necks are elongated with a stable posterior
region, possibly to enable them to carry out a precise throat bite.
With this new information on phylogeny and functional morphology gorgonopsian evolution can be re-
evaluated, which is essential for future studies on the group. However, more research and especially more
material is needed to make additional contributions to the knowledge of these saber-toothed predators.ii abstraCt