The periotic bones of possums and cuscuses: cuscus polyphyly and the division of the marsupial family Phalangeridae

Detailed examination of the periotic bones of ten species of phalangerid marsupials revealed the existence of three distinctive classes of periotic morphology, termed ailuropine, trichosurin and phalangerin. Cladistic analysis of fifteen characters of the periotic suggested the ailuropine periotic to be the most plesiomorphic in morphology, with the trichosurin and phalangerin periotics representing a more derived clade. This character distribution would support recent taxonomic schemes, in which the cuscuses are seen as a paraphyletic grouping: the greater and lesser Sulawesi cuscuses ( Ailurops ursinus and Strigocuscus celebensis ) exhibiting respectively ailuropine and trichosurin periotics, with all other cuscuses possessing phalangerin periotics. However, it does not support the assertions of some authors that the Moluccan cuscuses ( Phalanger ornatus and P. rothschildi ) and the ground cuscus ( P. gymotis ) are trichosurins.     

Additional data on early Paleocene metatherians (Mammalia) from Punta Peligro (Salamanca Formation, Argentina): comments based on petrosal morphology

Metatherian remains from Punta Peligro (Chubut Province, Argentina; Salamanca Formation, early Paleocene) are scarce, but at present, there are at least four different taxa known by dental remains. We describe here an incomplete petrosal showing metatherian affinities. Among the dentally known taxa from the same stratigraphic levels, the overall size of the petrosal fits that predicted for Derorhynchus , which in turn was assigned to the order Didelphimorphia. The features of the petrosal we describe do not correspond with the morphology observed among didelphoid marsupials, the only members of Didelphimorphia with well known basicrania, suggesting that if the association of petrosal and dental remains is correct, then referral of Derorhynchus to the Didelphimorphia has to be revised. The taxonomic content of this group of marsupials, as presently interpreted, represents a paraphyletic or polyphyletic grouping of metatherians.     

The unusual cranial attributes of KNM-ER 1805 and their implication for studies of sexual dimorphism inHomo habilis

A principal components analysis (PCA) of basicranial measurements (Thompson 1991) isolated KNM-ER 1805 as having the highest Principal Component (PC) score on PCI of all the fossil hominids. Two measurements with high loadings on PCI were B12 and B13 and these two measurements indicate the relative positions of the foramina ovale (FO) and infratemporal crests (IT) to the tympanic bone (TP). The object of this study was to compare the two measurements of KNM-ER 1805 with those of other early fossil hominids as well as a sample of extant hominoids. The comparison involved the raw measurements, the index of the two measurements, the coefficient of variation, and a t-test. The results of this comparison showed that KNM-ER 1805 had more forwardly placed foramina ovale than any of the comparative specimens. KNM-ER 1805 possesses a number of other unique features which differentiate it from other hominids including a persistent metopic suture, the form of the premolar roots, and the form of the asterionic region. These apparent unique features mean that KNM-ER 1805 is unlikely to represent an “average” maleHomo habilis and so is an inappropriate model for the male morph of that species.     

Patterns of evolutionary transformation in the petrosal bone and some basicranial features in marsupial mammals, with special reference to didelphids

Twelve petrosal and four nonpetrosal characters were coded for representatives of all 15 extant genera of Didelphidae and for 16 additional genera of marsupials representing all extant orders. Three basal metatherians were used as outgroup comparison. Histological sections of a subset of the data were examined. An intermediate position of the hiatus Fallopii supports the monophyly of Didelphidae. Several basicranial regions support different clades within the Didelphidae that recent molecular work has identified, including a sister group relationship of Caluromys and Caluromysiops , the monophyly of large opossums, a Lestodelphys-Thylamys clade, and a Lestodelphys-Thylamys-Gracilinanus-Marmosops clade. Glironia lacks petrosal and jaw synapomorphies of Caluromys and Caluromysiops. The transverse canal, a synapomorphy of the crown-group Marsupialia, opens as a single foramen anterior to the carotid foramen in most marsupials or as numerous foramina in the pterygoid fossa in diprotodontians. It is either intramural (most marsupials) or simply endocranial (most diprotodontians excluding koalas and wombats). Loss of a deep sulcus in the anterior pole of the promontorium for the internal carotid artery and a rostral tympanic process of the petrosal also characterize the groundplan of the crown group Marsupialia. Pouch-young wombats show a groove in the anterior pole of the petrosal for the internal carotid artery. The absence of a prootic canal foramen in the tympanic side of the petrosal of adults supports the monophyly of Australidelphia. Some pouch-young marsupials possess a prootic canal that is later lost in ontogeny. A rather flat promontorium and a crest running medio-distally in the middle of the promontorium characterize Macropodidae.     

The middle ear of the skull of birds: the Pelecaniformes and Ciconiiformes

The anatomy of the middle ear region of the skull is described for the families of the Avian orders Pelecaniformes and Ciconiiformes. Emphasis is placed on the foramina and paths of the nerves and blood vessels. The morphology of the basicranium and quadrate is also discussed. Comparative analyses of the characters are used to assess taxonomic conclusions.
Extant Pelecaniformes consist of six families, four of which are monogenic: Phaethontidae, Pelecanidae, Anhingidae and Fregatidae; one is composed of two genera: Sulidae; and the last has three genera: Phalacrocoracidae. Several years ago a relationship was suggested which would ally the Phaethontidae and the Fregatidae. While these families share several non middle ear characters the anatomy of the middle ear is not compatible with any particular relationship. Indeed, several obvious differences are described. The data presented here are consistent with the idea that the Phaethontidae and the Fregatidae each form a separate group of Pelecaniform birds, with the rest of the families forming a third group. Several differences in the middle ear region of the species of Anhingidae suggest that the family may be composed of two genera.
While sharing many Ciconiiform characters the Ciconiidae have been shown not to be as closely related to the Ardeidae as they are to other families of Ciconiiformes. In addition, evidence is presented to support the recent idea that the three species of ibis (I. ibis, I. cinereus and I. leucocephalus ) be united within the genus Mycteria. Also supported is the notion that Balaeniceps is Pelecaniform in character, and not Ciconiiform.     

Sexual dimorphism in primates: Where are we and where do we go from here?

There are currently several debates taking place in palaeoanthropological circles in which the issue of sexual dimorphism is crucial. During the 60th Jubilee of the discovery of the TaungAustralopithecus skull, the authors concurred that much of the debate was due to differences in perception concerning dimorphism, and it was suggested that a study session dealing principally with sexual dimorphism in Primates should be organised with a view to determining what, if anything, could be observed in extant primates that might be utilised for determining the existence of dimorphism in fossil species. An advertisement was placed in the Journal of Human Evolution, calling for papers. Response was encouraging, suggesting that there was indeed a need for such a meeting, which was organised to take place late in November in Italy. Seventeen scientists sent abstracts, but due to the rather short notice, several were unable to attend the meeting. Nevertheless, papers were received and read at the meeting which form the basis for this issue of the Journal of Human Evolution. What remains to be done now, is for a second meeting to be organised at which the findings of the first meeting can be extended backwards in time into the fossil record.     

The human axillary organ: An evolutionary puzzle

In the cavum axillae of humans lies a glandular organ composed of tightly packed apocrine glands with secrete a colourless, or slightly pigmented fluid — the so-called axillary organ. It develops during childhood but remains inactive until the onset of sexual maturity when it grows hairs and embarks on a lifetime of secretion. A similar structure occurs in African apes but in no other Primates. Being equally well-developed in males and females the axillary organ is not a secondary sexual characteristic, even though it produces secretions rich in steroidal compound relating to sex and sexual status. It is argued that, with the development of gregariousness, the brain’s recognition template for odorous oestrus advertisement was blocked in order to protect the bond between parents which was necessary for ensuring maximum offspring survival. The axillary organ took on a new role, namely to provide odorous stimulation for strengthening the pairbond, and lost its previous role as advertiser of individuality.     

A commentary on Ridley's cladistic solution to the species problem

The cladistic species concept proposed by Ridley (1989) rests on an undefined notion of speciation and its meaning is thus indeterminate. If the cladistic concept is made determinate through the definition of speciation, then it reduces to a form of whatever species concept is implicit in the definition of speciation and fails to be a truly alternative species concept. The cladistic formalism advocated by Ridley is designed to ensure that species are monophyletic, that they are objectively real entities, and that they are individuals. It is argued that species need not be monophyletic in order to be real entities, and that ancestor-descendant relations are not the only relations that confer individuality on entities. The species problem is recast in terms of a futile quest for a definition of that single kind of entity to which the term species should uniquely apply.     

Paternity exclusion in primates: Two strategies

Two strategies for the use of polymorphic biochemical and serological markers in paternity testing problems in non-human primate groups, where pedigree information is incomplete, are discussed. The positive approach, of attempting to prove paternity, is shown to be impracticable given the levels of detectable genetic variation among primates. The more conventional approach of paternity exclusion is examined and found to be useful under certain conditions. This approach is illustrated using the published data on the levels of biochemical and serological variation in Macaca nemestrina.