Jaw Fragments Research Articles

A new species of Purgatorius (Mammalia; Primatomorpha) from the Lower Paleocene Bear Formation, Crazy Mountains Basin, south-central Montana

Purgatorius titusi, represented by 51 teeth and jaw fragments, is described from the lower Paleocene Bear Formation of the Crazy Mountains Basin in south-central Montana. Several synapomorphies, including a weak postprotocingulum and mesial inflection of molar trigonids, are indicative of the taxon's “plesiadapiform” affinities. Other features, such as wider stylar shelf and a less squared lingual outline on upper molars, are more primitive than those of Purgatorius unio, heretofore the earliest occurring species of well-represented primatomorphs.

Systematics and taxonomic diversity of squamates from the Upper Cretaceous Djadochta Formation, Bayan Mandahu, Gobi Desert, People's Republic of China

Squamate fossils collected for the Sino-Canadian dinosaur expeditions (1986–1990) include some 70 specimens from the Upper Cretaceous (Campanian) Djadochta Formation, exposed at the vicinity of Bayan Mandahu, Inner Mongolia, China. Well-preserved skulls, jaws, postcranial skeletons, and even osteodermal armor document a fossil assemblage composed of at least 18 genera in 8 families. Besides showing considerable taxonomic diversity, several families recorded in the assemblage are of importance in understanding the geologic and biogeographic distribution of the relevant groups, and the paleoenvironment in which these lizards lived. Comparison of the Gobi lizard assemblage with North American and Central Asian assemblages is briefly discussed. Taxonomic differences in the assemblage from that of the Upper Cretaceous in the North American Western Interior reflect endemism and suggest a low frequency of interchange of small terrestrial vertebrates between the two regions during Campanian time. The taphonomic setting of the squamate fossils indicates quick burial in arid to semiarid environments in the Gobi Desert, differing importantly from the Western Interior of North America, where the accumulation of disarticulated jaw fragments reflects postmortem decomposition and fluvial transportation under subtropical to warm temperate conditions.

Genetic and Morphological Records of the Hominoidea and Hominid Origins: A Synthesis

Molecular genetics has had a major impact on phylogenetics, although many hominoid paleontologists and morphologists ignore or remain unaware of genetic data. However, substantial genetic evidence shows chimpanzees and humans as closest relatives. Living hominoids share many postcranial similarities, many of which are retained from the extant hominoid common ancestor. Miocene hominoid fossils consisted until recently mostly of teeth and jaw fragments which are relatively uninformative phylogenetically. As their postcrania have become better sampled, surprisingly few of these taxa share significant similarities with living apes, suggesting that few if any are related to specific extant lineages. Given the genetically inferred relationships of hominoids and the morphology of the earliest hominids, the common ancestor of humans and chimpanzees was probably chimp-like, a knuckle-walker with small thin-enameled cheek teeth. If correct, this scenario implies that known Miocene hominoids, most of which are postcranially archaic and have large, thickly enameled cheek teeth, throw little if any direct light on hominid origins.

New primate from the Palaeogene of Thailand, and the biogeographical origin of anthropoids

Abstract Recent field work in the Eocene Krabi Basin (south Thailand) has yielded a fragment of a primate lower jaw containing the second and third molar teeth attributed to a new genus and species, Wailekia orientale. The specimen described here is morphologically very close to Oliopithecus savagei from the Fayum (Egypt), and the presence of Wailekia in the Upper Eocene of Thailand suggests that South East Asia may be an important centre of origin for anthropoids.

CLINICAL MANAGEMENT OF INJURIES TO THE MAXILLA, MANDIBLE, AND ALVEOLUS

Facial bone and especially mandibular fractures are injuries in which first aid and management of late complications require dental professionals, and consequently all dentists should be familiar with the modern principles of their treatment. Tooth involvement is common in mandibular and maxillary fractures and can require more treatment than does the jaw fracture. Nonsurgical treatment of bone fractures involves immobilization, which for the facial bones is achieved with maxillomandibular fixation (MMF) using dental fixed arch bars. Hence, associated tooth injuries are difficult or impossible to treat during immobilization, so that some treatment is necessary beforehand (for example, coverage of exposed dental areas, temporary filling of crown fractures, repositioning of luxated teeth, and endodontic treatment if the pulpal vascular supply is lost in the accident). Operative treatment of mandibular and/or maxillary fractures nevertheless involves some disadvantages and risks of complications. Teeth on the line of a mandibular fracture should not be extracted as a first-aid measure unless they impair repositioning of the jaw fragments. MMF can be avoided by means of direct internal fixation, which in principle allows treatment of associated dental injuries.

The First Tetrapod Finds from the Devonian (Upper Famennian) of Latvia

Ventastega curonica, from the Upper Famennian Ketleri Formation, is the first tetrapod find from the Upper Devonian of Latvia, and only the fourth adequately represented Devonian tetrapod genus to be described. The taxon is represented by disarticulated cranial and postcranial elements from two localities, Ketleri on the Venta River and Pavari on the Ciecere River. A second tetrapod, represented by a single mandibular fragment, appears to be present at Ketleri. The lower jaw of Ventastega is strikingly primitive in retaining fangs on the coronoid series, but shares many characters with those of other known Devonian tetrapods. Some of these features are interpreted as basal tetrapod synapomorphies; they provide a new data set for the identification of isolated tetrapod jaw fragments, and confirm the (previously disputed) tetrapod status of Metaxygnathus. The upper jaw bones of Ventastega are broadly similar to those of Acanthostega, Ichthyostega and Tulerpeton, as is the narial region. The lateral rostral bone is either very small or absent. A preopercular bone is present in the cheek, and the lacrimal is excluded from the orbit. The palate is closed. Palatine and vomer bear fangs which are set in the marginal tooth row. An isolated iliac blade from Pavari, probably attributable to Ventastega, resembles that of Acanthostega but may not have carried a dorsal process. Two clavicles from Pavari and Ketleri which may also belong to Ventastega are of a typical early tetrapod pattern, similar to Greerpeton but with a broader ventral blade. Non-attributable or doubtfully attributable bones from Ketleri include a probable tetrapod postorbital and a possible limb bone. Ventastega appears to be a tetrapod of the same broad `grade' as Ichthyostega and Acanthostega, but is arguably more primitive than either.

Relations among the great apes and humans: New interpretations based on the fossil great apeDryopithecus

Dryopithecus has been known longer than most fossil primate taxa, but until recently was only represented by fragmentary jaws and isolated teeth. New specimens, including postcrania and relatively complete cranial remains, provide much new evidence on the biology of Dryopithecus and its relations t o other primates. The phylogenetic evidence indicates that Dryopithecus is probably more closely related to the African apes and humans than is Sivapithecus. When compared closely to living forms, Dryopithecus shares more with gorillas. This does not imply a close relationship between Dryopithecus and gorillas, since the similarities between the two are all primitive characters. Instead, it suggests that chimps and humans, which lack these characters, share a series of alternative character states that are derived, and indicative of a close evolutionary relationship between them. Humans probably diverged from a very chimp-like ancestor characterized by much of the ecology and behavior of living chimps, including knuckle-walking. But the earliest humans must have been ecologically quite distinctive, and not very much like any living primate, to account for the dramatic morphological changes that mark human origins. © 1994 Wiley-Liss, Inc.

A new procolophonid and a new tetrapod of uncertain, possibly procolophonian affinities from the Upper Triassic of Virginia

ABSTRACT Two jaw fragments of small tetrapods from the Turkey Branch Formation of the Richmond basin (Newark Supergroup; Upper Triassic: lower to middle Carnian) of Virginia have highly distinctive dentitions. The robust, transversely broadened, and bicuspid teeth of Gomphiosauridion baileyae, gen. et sp. nov. support its placement in the Procolophonidae. The two cusps are linked by a pronounced transverse ridge, which divides the occlusal surface of the crown into two deep fossettes. The cusps have strongly fluted enamel. The heterodont dentition of Xenodiphyodon petraios, gen. et sp. nov. comprises transversely broadened, tricuspid posterior teeth and transversely compressed anterior teeth with distinct apical ridges. The posterior teeth of Xenodiphyodon closely resemble those of the alleged trilophosaurid taxa Tricuspisaurus thomasi and Variodens inopinatus from Upper Triassic fissure-fillings in southwestern England and ?Trilophosaurus jacobsi from the Upper Triassic Chinle Formation of Arizona. The l...

Application of DNA techniques for identification using human dental pulp as a source of DNA

Dental pulp tissue could be obtained in most cases from materials obtained under experimental conditions and from forensic casework (air accidents, burned and putrefied bodies). Teeth extracted during dental treatment (n = 30) were stored for 6 weeks and 4 years at room temperature. In addition teeth (n = 10) extracted from jaw fragments that had been stored for 15 years at room temperature, and teeth extracted post mortem from actual identification cases (n = 8) were investigated. Following extraction from dental pulp tissue the DNA concentration was measured by fluorometry. The amount of DNA obtained from the dental pulp tissue of a single tooth varied from 6 micrograms to 50 micrograms DNA. In most cases high molecular weight DNA was still present although the major portion consisted of degraded DNA. Genomic dot blot hybridization for sex determination using the biotinylated repetitive DNA probe pHY 2.1 was performed and sex was correctly classified in all cases using 50-100 ng target DNA. PCR typing of the HLA-DQ alpha and ApoB 3' VNTR systems from dental pulp tissue DNA was in agreement with the results obtained from blood, bloodstains, or lung tissue. In addition, Southern blot analysis of selected samples using the single locus VNTR probe pYNH24 was successfully performed. In all cases the DNA recovered from dental pulp was unsuitable for multilocus probe analysis.

An additional record of a placental mammal (Order Astrapotheria) from the Eocene of West Antarctica

Recently, fossil land mammals have been recorded in the James Ross Island area, east of the Antarctic Peninsula, from the marine middle-late Eocene strata of Seymour Island. These include two endemic species of polydolopid marsupial: Antarctodolops dailyi Woodburne & Zinsmeister 1984, and Eurydolops seymourensis Case, Woodburne & Chaney 1988, and three partly determinate placentals identified as a tardigrade edentate, a sparnotheriodontid litoptern and a trigonostylopid astrapothere (Bond et al. 1989). The marsupials are represented by fragmentary jaw and complete dental material, the litoptern and astrapothere only by tooth fragments. All are recorded from Unit TELM 5 of the La Meseta Formation (Sadler 1988), the two ungulates at a lower level than the rest. The subject of the present note is a second tooth fragment from Seymour Island identified as an astrapothere. It is worth recording because such mammal remains are rare and it is from TELM 4, the unit below that yielding the other land mammals.

Evidence for Attacks by the Bathypelagic Fish Anotopterus pharao (Myctophiformes) on Pacific Salmon (Oncorhynchus spp.)

Adult Pacific salmon (Oncorhynchus spp.) returning from offshore waters to spawn frequently bear a wide range of wounds and scars. One of the most common wounds is a single slash mark on the posterior third of one side of the body, running posteroventrally from near the dorsal fin at a roughly 45° angle. The evidence is reviewed for the occurrence of slash-marked salmon around the Pacific Rim over the past 30 yr. A jaw fragment removed from the wound of a slash-marked sockeye salmon (O. nerka) and identified as belonging to a daggertooth (Anotopterus pharao: order Myctophiformes), a highly modified bathypelagic fish, provides the first direct evidence for the cause of these wounds. Given the frequency of slash-marked adult salmon in coastal fisheries, A. pharao may be a significant cause of mortality in Pacific salmon that has previously gone unrecognized.

A labyrinthodont jaw fragment from the marine Triassic of the Alps

A labyrinthodont jaw fragment from the marine Triassic of the Alps

A bone bed in the Eocene of Jamaica

Pre-pleistocene fossil vertebrates are rare fossils in the Antillean region. The majority of vertebrate deposits found in the West Indies are of Late Pleistocene age, usually, but not always (MacPhee et al., 1989), dating from after the last interglacial. These faunas are cave and fissure accumulations of disarticulated bones of small terrestrial vertebrates, particularly rodents, birds, and lizards. In contrast, pre-Quaternary vertebrates of the Caribbean islands are particularly poorly known. For example, Jamaica, which has one of the most extensively studied fossil records in the region, has hitherto produced only three Tertiary vertebrates, all aquatic and hitherto known only from unique specimens. These include: the late Early Eocene sirenian Prorastomus sirenoides Owen, 1855, originally described on the basis of the skull, mandible, and atlas vertebra (for a recent discussion of this species, see Savage, 1977); the lower jaw of the early Middle Eocene crocodilian Charactosuchus kugleri Berg, 1969; and a fragment of needlefish jaw from the Pliocene (Caldwell, 1966). It is therefore significant to report the discovery of an early Middle Eocene sequence in which bones are not uncommon, including a bone bed that has produced a moderate diversity of aquatic (marine?) taxa.

The skull of Cteniogenys, a choristodere (Reptilia: Archosauromorpha) from the Middle Jurassic of Oxfordshire

The genus Ctemogenys was originally described as a lizard on the basis of isolated jaw fragments from the Upper Jurassic deposits of Como Bluff, Wyoming. The discovery of new material from a Middle Jurassic locality at Kirtlington, Oxfordshire, showed that Cteniogenys was not a lizard, but an early choristodere. The skull is represented by a collection of isolated bones, associated on the basis of fit and dermal sculpture pattern. The bones are here described and compared with those of the Late Cretaceous and Palaeocene choristoderes Champsosaurus and Simoedosaurus. Allowing for the much smaller size of the Middle Jurassic form, there is a close correspondence between the isolated bones of the three genera. Comparison with known choristoderes, based on an analysis of 53 derived character states, suggests that Ctemogenys is the most primitive of known genera. In general, the character states shared by all choristoderes support recent analyses which conclude that choristoderes arc derived from archosauromorph diapsids, not lepidosauromorphs as once thought. At Kirtlington, Cteniogenys forms part of a diverse microvertebrate assemblage including amiids, sharks, frogs, salamanders, lizards, mammals, crocodiles, pterosaurs, turtles and small dinosaurs.

Eutherian mammals from the Early Cretaceous of Mongolia

A collection of eutherian mammals consisting of 39 specimens (teeth and jaw fragments) from the ?Aptian or Albian Khoboor Beds in the Gobi Desert, Mongolia, is described. It contains 3 taxa: Prokenna1estes gen.n., assigned to the Otlestidae Nessov, new rank, with 2 shrew size species; P. trofimovi sp.n. and P. minor sp.n.; a heavily worn larger lower molar which will be described elsewhere. It cannot be excluded that P. trofimovi and P. minor are only sexual morphs within the same species. Prokennalestes and Bobolestes Nessov are possibly the oldest known eutherian mammals, but Prokennalestes is morphologically more primitive than Bobolestes. It has a labial mandibular foramen, 5 premolars and 3 molars, 3 cusps in parastylur region, paracone larger than metacone, unwinged conules, no pre‐ and posteingula, and lower molars with a 3‐cusped talonid, which is narrower than the trigonid, Otlestes and Kennalestes may be derived with little modification from Prokennalestes. Prokennalestes gen.n. is congeneric with Prokennalestes Trofimov and Prozalambdalestes Trofimov, which are both nomina nuda.

Mammal teeth from the Cretaceous of Africa.

We report here the discovery of two mammal teeth from the early Cretaceous of Cameroon. These, and some jaw fragments, all from Cameroon, are the only fossil evidence of mammalian evolution from Africa between late Jurassic and Paleocene, a span of at least 85 million years. A triangular upper tooth lacks the principal internal cusp of marsupials and placentals and is therefore of a similar evolutionary grade to most Jurassic and early Cretaceous therian mammals, but more primitive than the metatherian-eutherian grade. Early Cretaceous, or older, therian mammals are now known from all southern continents except Antarctica. The new find from Cameroon is consistent with the hypothesis that marsupials, the dominant living mammals of South America and Australia, were not present on any Gondwana continents until after the early Cretaceous separation of Africa by the opening of the South Atlantic.

Phytosaur remains from the Cenger Formation of the Lycian Taurus (western Turkey): Stratigraphical implications

The red arkosic sandstones of the Cenger Formation, in the allochthonous units of the Lycian Taurus (western Turkey), which had already yielded a small ichthyofauna, have yielded fragmentary remains (teeth, jaw fragments, vertebrae) of archosaurian reptiles. Among these, phytosaur remains can be recognised; they are too incomplete to warrant an accurate identification, but they do provide biostratigraphical data, since they indicate a Late Triassic age. The reptile remains from the Cenger Formation thus confirm the stratigraphical conclusions previously drawn from the study of lungfishes, and increase our knowledge of the geographical distribution of Gondwanan phytosaurs.

New reptiles from the Upper Triassic Chinle Formation of Arizona

New records of Late Triassic reptiles from the Chinle Formation of Arizona include a new species of small trilophosaurid, a sphenodontid, and two taxa of eolacertilians. ?Trilophosaurus jacobsi n. sp. is a small trilophosaurid showing affinities to the type of Trilophosaurus buettneri of the southwestern United States and Variodens inopinatus from the Upper Triassic of Great Britain. A sphenodontid is also reported along with maxillae tentatively referred to the Kuehneosauridae and a jaw fragment from a subpleurodont eolacertilian with polycuspate teeth.

The origin of egg-laying mammals

The origin of monotremes—egg-laying mammals from the Australian region—and their relationship to therians (marsupials and placentals) have been intriguing zoological problems. Recently Archer et al.1 described a fragment of a lower jaw of an early Cretaceous monotreme from Australia (Steropodon galmani) and interpreted its teeth as tribosphenic and thus supposedly derived from a relatively advanced stage in therian evolution. This discovery is of major importance, and radically alters currently held opinion that monotremes and therians diverged at the earliest stage of mammalian evolution. We agree that Steropodon is a therian but would argue thai its teeth are not tribosphenic. Steropodon appears to have been derived from therians before the development of tribosphenic teeth, possibly during the Jurassic period.

Eocene mammals from the Upper Subathu Group, Kashmir Himalaya, India

New finds of brontotheres, raoellid artiodactyls and cetaceans are reported from the Middle Eocene Upper Subathu Group exposed in the Kalakot-Metka-Moghla inliers of Rajauri District, Jammu and Kashmir. The brontothere is closely allied to Eotitanops dayi from the Ganda Kas region of Pakistan and is much smaller than Pakotitanops. Raoellids are represented by four genera and five species including Metkatius kashmiriensis, gen. et sp. nov. and Kunmunella transversa, sp. nov. The Eocene artiodactyls of India do not resemble contemporary forms from contiguous regions and are probably endemic to the subcontinent. The systematics of previously described Indo-Pakistani genera have been revised and listed. Associated mammals include a jaw fragment of a protocetid whale, Ichthyolestes pinfoldi, which is also known from coeval beds in Pakistan.