Triassic Biostratigraphy Research Articles

CONODONTS: PAST, PRESENT, FUTURE

Conodonts were mostly small, elongate, eel-shaped marine animals that inhabited a variety of environments in Paleozoic and Triassic seas. Although long enigmatic, conodonts are now regarded as vertebrates and their closely controlled fossil record is not only the most extensive of all vertebrates, but it also makes conodonts the fossils of choice in upper Cambrian through Triassic biostratigraphy. Conodonts were soft-bodied except for a variety of phosphatic elements that formed a distinctive feeding apparatus. Post-mortal dissociation of the apparatus and subsequent jumbling of its elements on the sea floor led, from 1856 to about 1966, to development of an artificial, form-based taxonomy that was utilitarian, but clearly unsatisfactory as a vehicle for understanding the group in biologic terms. Natural assemblages of elements, discovered between 1879 and 1952, have been interpreted as undisturbed skeletal apparatuses, and in the mid-1960s it was determined that original composition of the apparatuses of many species could be reconstructed and statistically evaluated from collections of disjunct elements by various grouping procedures. These determinations led to an emphasis on multielement taxonomy by most (but not all) students of conodonts. Even so, only about a third of the approximately 550 valid conodont genera, have been established (or re-interpreted) in multielement terms and this makes any of the several extant schemes of suprageneric classification phylogenetically suspect. We comment on a recent scheme that recognizes 41 families assigned to some 7 orders, and suggest how it might be modified so as to square with principles of phylogenetic systematics.

Upper Triassic Biostratigraphy and Algae from Žumberak (Croatia)

In the Upper Triassic dolomite deposits of the Žumberak region(west of Zagreb, Croatia) the following local biostratigraphic zonesare distinguished: Clypeina besici Taxon-range zone (Carnian). Aulotortus sinuosus.Interval-zone (Norian), and Triasina hantkeni Taxonrangezone (Rhaetian). Dasycladal algae Clipeina besici (PANTIC), Griphoporella curvata (GUEMBEL), Physoporella jomdalensis FLUEGEL & MU and Acciulella sp. are accurately described.

Bio-stratigraphy and correlation of the marine Triassic of the Sepharadic province.

Bio-stratigraphy and correlation of the marine Triassic of the Sepharadic province.

Thalassinid anomuran microcoprolites from Upper Triassic carbonate rocks of central Peru

Within the Upper Triassic-Jurassic sequence of the Pucara Group of central Peru the tiny fecal pellets (microcoprolites) of anomuran crustaceans are locally very abundant. They occur in burrowed, micritic and bioclastic, shallow water carbonate rocks together with fragments of molluscs and other benthic invertebrates. Three of these, Palaxius salataensis Bronnimann, Caron & Zaninetti, Parafavreina thoronotensis Bronnimann, Caron & Zaninetti and Parafavreina huaricolcanensis n. sp. are described from the Upper Triassic (Norian) Chambara Formation in central Peru. This is the first description of such microcoprolites in South America and their discovery provides new insight into Triassic biostratigraphy and paleogeography in this part of the world.

Conodonts and Biostratigraphic Correlation

At its 1969 meeting, The Pander Society convened a symposium on conodont biostratigraphy that resulted in a volume (Sweet & Bergstrom 1971a) in which specialists systematically summarized the status of conodont-based biostratigraphy up to 1969. One function of such a volume is to direct attention to areas that need more work and to focus on conclusions in need of more robust verification. The Pander Society's biostratigraphy volume provides this focus and has also been a very useful guide to the biostratigraphic uses of conodonts. In the 14 years since the volume appeared, additional effort has been expended on then-tentative biostratigraphic schemes, and revised or alternative biostratigraphic scales have been stimulated for several intervals. We cannot hope in this review to bring the Pander Society's bio­ stratigraphy volume fully up to date, or even to review all major lines of progress in conodont-based biostratigraphy of the past 14 years. What we can do is note major changes offairly recent vintage, with emphasis on areas in which the application of different correlation algorithms has confirmed systems that were apparently well established in 1971, or in which use of different correlation methodology has resulted in a different view of these systems. Our discussion deals largely with Ordovician and Triassic biostratigraphy, our areas of expertise, and with the contrast in those areas between the results of traditional biozonal practices and those of less conventional graphic procedures.

On the discovery of Glyptophiceras from the Hiraiso Formation (Lower Triassic) in the Kitakami Massif and a Note on the Lower Triassic biostratigraphy

On the discovery of Glyptophiceras from the Hiraiso Formation (Lower Triassic) in the Kitakami Massif and a Note on the Lower Triassic biostratigraphy