Estudo comparativo entre os sincrânios de Otaria byronia e Arctocephalus australis (Pinnipedia, Otariidae)

Abstract

Iheringia, Sér. Zool., Porto Alegre, 98(1):5-16, 30 de março de 2008 Estudo comparativo entre os sincrânios de Otaria byronia e... Estudo comparativo entre os sincrânios de Otaria byronia eArctocephalus australis (Pinnipedia, Otariidae) ABSTRACT. Comparative study between the syncranium of Otaria byronia and Arctocephalus australis (Pinnipedia, Otariidae). A high degree of anatomical variability in many structures of Otaria byronia (Blainville, 1820) and Arctocephalus australis (Zimmerman, 1783) was observed, which should yield serious implications to the systematics of Otariidae. The main differences observed between the two species were: the breadth of the rostrum, the exposure (or not) of the ethmoid in the orbit, the palatine/pterygoid vacuity, the extension of the maxilla, the concaveness and shape of the palate, the size/shape of the orbit/supra-orbital process, the height/shape of the zygomatic arch, the shape of the hamulus pterygoideus, the size of processes and crests, the proportions of the sphenoid and of neurocranium, the occurrence or not of the vidian and transverse canals, the relieves of the cranial fossae, and the size of secondary angular process. While some differences (ethmoid) are rather unusual between contemporary species belonging to the same family, many others are of allometric nature. Some differences are peramorfic: skull size, palate size and crests size (hypermorphic in O. byronia).Others caracters are pedomorphic in this species: incisive foramen, maxille process of the frontal and vidian channels. The main differences between males and females of O. byronia, and similitarities between de males of this species and A. australis are related to developmental modification in rate or in the timing too. Some characters usually used in the group's systematics were not corroborated, mostly those related to the naso-labialis fossa; zygomatic-temporal suture; internal acoustic meatus and entotimpanic.KEYWORDS. Syncranium, anatomy, osteology, South American sea lion, South American fur seal. RESUMO.Observou-se grande variabilidade anatômica no sincrânio de Otaria byronia (Blainville, 1820) e de Arctocephalus australis (Zimmerman, 1783), com correspondentes implicações na sistemática dos Otariidae. As principais diferenças observadas entre as duas espécies foram a largura do rostro, exposição (ou não) do etmóide na órbita, vacuidade palatino/pterigóide, extensão do maxilar, concavidade e forma do palato, tamanho/forma da órbita/processo supra-orbital, altura/forma do palato, tamanho/forma da órbita/ processo supra-orbital, altura/forma do arco zigomático, forma do hâmulo pterigóide, tamanho de processos e cristas em geral, esfenóide e neurocrânio; presença ou não do canal vidiano e transverso; forma do pétreo e proporções do processo angular secundário. Enquanto algumas diferenças (etmóide) são bastante incomuns entre espécies contemporâneas pertencentes à mesma família, muitas outras são de natureza alométrica. Algumas diferenças são peramórficas: tamanho do crânio, do palato e das crista...

Interpretation of anatomical characters in phylogenetic analysis of Pinnipedia, with emphasis on Otariidae (Mammalia, Carnivora)

“…This confirms the necessity for more extensive and detailed studies of South American species, including large sample sizes, as recommended by Berta and Churchill (2012). Sanfelice and Ferigolo (2008) emphasized the high variability of skull characters in O. byronia and A. australis, refuting many character states previously used in the phylogenetic analysis of pinnipeds. In this context, these authors concluded that a comparative osteological study of all other otariids will certainly be very useful to the solution this problem and to the revision of the characters.…”

“…In addition, there is limited knowledge about the anatomy of several species (examples of skull descriptions in HOWELL, 1929;SIVERTSEN, 1954;REPENNING et al, 1971;KING, 1983;ANDREESCU;MURARIU, 1985;KASTELEIN;GERRITS, 1990;FERIGOLO, 1996a;MIZUNO;OHTAISHI, 2002;SANFELICE;FERIGOLO, 2008), and the frequent variability in the cranial (NOJIMA, 1990), postcranial (ROBINETTE;STAINS, 1970;ENGLISH, 1977) and dental (DREHMER; FERIGOLO, 1996b;DREHMER et al, 2004;CRUWYS;FRIDAY, 2006;LOCH et al, 2010) character states, which makes it even more difficult to clarify the relationships of this group.…”

Do cranial suture age and growth layer groups correlate in South American pinnipeds?

“…The first study that used the CSA method to estimate the age categories for the pinnipeds found dead in southern Brazil, was Simões-Lopes et al (1995), but they did not compare this with the specimens' GLGs. For the same geographic area several studies were carried out, but over an increased sample; Drehmer & Ferigolo (1996) applied this technique for A. australis skull description; Drehmer & Ferigolo (1997) in a comparative analysis including A. australis and A. tropicalis and Sanfelice & Ferigolo (2008) for A. australis and Otaria flavescens . The CSA method had also been used for several decades in humans in forensic medicine (Meindl & Lovejoy, 1985).…”

Pinniped turnover in the South Pacific Ocean: new evidence from the Plio-Pleistocene of the Atacama Desert, Chile

“…The marginal process (sensu Davis, 1964; = secondary angular process in Sanfelice and Ferigolo, 2008) is strongly projected dorsally, and its posterior border has a triangular shape. A well-developed marginal process is also present in Odobenidae (Deméré, 1994); nevertheless, it is useful to discriminate among otariids because in Arctocephalus it is barely patent, whereas in Otaria it is well developed (Sanfelice and Ferigolo, 2008). Therefore, the presence of a well-developed marginal process and the presence of a sinuous ventral margin of the horizontal ramus allows us to identify this specimen as Otaria.…”