Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

D. B. Owen: Handbook of Statistical Tables. London: Pergamon Press; Reading, Massachusetts: Addison‐Wesley, 1962. Pp. xii+580. 70s.

Handbook of Statistical Tables.

A simple equilibrial model for the growth and maintenance of Phanerozoic global marine taxonomic diversity can be constructed from considerations of the behavior of origination and extinction rates with respect to diversity. An initial postulate that total rate of diversification is proportional to number of taxa extant leads to an exponential model for early phases of diversification. This model appears to describe adequately the “explosive” diversification of known metazoan orders across the Precambrian-Cambrian Boundary, suggesting that no special event, other than the initial appearance of Metazoa, is necessary to explain this phenomenon. As numbers of taxa increase, the rate of diversification should become “diversity dependent.” Ecological factors should cause the per taxon rate of origination to decline and the per taxon rate of extinction to increase. If these relationships are modeled as simple linear functions, a logistic description of the behavior of taxonomic diversity through time results. This model appears remarkably consistent with the known pattern of Phanerozoic marine ordinal diversity as a whole. Analysis of observed rates of ordinal origination also indicates these are to a large extent diversity dependent; however, diversity dependence is not immediately evident in rates of ordinal extinction. Possible explanations for this pattern are derived from considerations of the size of higher taxa and from simulations of their diversification. These suggest that both the standing diversity and the pattern of origination of orders may adequately reflect the behavior of species diversity through time; however, correspondence between rates of ordinal and species extinction may deteriorate with progressive loss of information resulting from incomplete sampling of the fossil record.

A kinetic model of Phanerozoic taxonomic diversity I. Analysis of marine orders

Current information on the conodonts Clydagnathus windsorensis (Globensky) and Promissum pulchrum Kova! cs‐ Endro$ dy, together with the latest interpretations of conodont hard tissues, are reviewed and it is concluded that sucient evidence exists to justify interpretation of the conodonts on a chordate model. A new phylogenetic analysis is undertaken, consisting of 17 chordate taxa and 103 morphological, physiological and biochemical characters; conodonts are included as a primary taxon. Various experiments with character coding, taxon deletion and the use of constraint trees are carried out. We conclude that conodonts are cladistically more derived than either hagfishes or lampreys because they possess a mineralised dermal skeleton and that they are the most plesiomorphic member of the total group Gnathostomata. We discuss the evolution of the nervous and sensory systems and the skeleton in the context of our optimal phylogenetic tree. There appears to be no simple evolution of free to canal-enclosed neuromasts; organised neuromasts within canals appear to have arisen at least three times from free neuromasts or neuromasts arranged within grooves. The mineralised vertebrate skeleton first appeared as odontodes of dentine or dentine plus enamel in the paraconodont}euconodont feeding apparatus. Bone appeared later, co-ordinate with the development of a dermal skeleton, and it appears to have been primitively acellular. Atubular dentine is more primitive than tubular dentine. However, the subsequent distribution of the dierent types of dentine (e.g. mesodentine, orthodentine), suggests that these tissue types are homoplastic. The topology of relationships and known stratigraphic ranges of taxa in our phylogeny predict the existence of myxinoids and petromyzontids in the Cambrian.

Conodont affinity and chordate phylogeny

Modes of fossil preservation

A fossil hagfish (Myxinoidea), a new genus from the Pennsylvanian, shows tentacles, structures of the head skeleton and internal organs. No other fossils of this group have been reported. Although this new hagfish differs from living forms in position of the gills, feeding apparatus, and relatively well developed eyes, it is quite similar to its recent relatives. Thus, hagfishes have a long, conservative geological history. Cladograms showing myxinoids as a sister group to the vertebrates are supported.

https://science.sciencemag.org/content/sci/254/5032/701.full.pdf

First fossil hagfish (myxinoidea): a record from the pennsylvanian of illinois.

A fossil record of lampreys has previously been unknown. A new genus demonstrates the presence of this group in the Pennsylvanian. The body outline, parts of the head skeleton, rasping tongue mechanism, gill basket, and other internal organs are preserved. The fossils are very similar in structure to modern forms. The absence of hagfish characters in the fossil supports the view that the common ancestor of lampreys and hagfishes lived prior to the Pennsylvanian.

https://science.sciencemag.org/content/sci/162/3859/1265.full.pdf

First Fossil Lamprey: A Record from the Pennsylvanian of Illinois

Seven palaeonisciform species can be recognized in the Middle Pennsylvanian Mazon Creek fauna of Illinois, U.S.A. Two of the five “Elonichthys” species with denticulated scales are new, “E.” wolffi, n.sp. and “E.” remotus, n.sp.; “E.” perpennatus Eastman, 1903, is a juvenile form and a synonym of “E.” hypsilepis Hay 1900. Two new species with smooth scales are placed in new genera: Illiniichthys cozarti, n.g. et sp., and Nozamichthys contorta n.g. et sp. “E.” peltigerus and “E.” hypsilepis are by far the most common palaeonisciforms in the Mazon Creek fauna and specimens of different stages of juvenile development occur. Most may be assigned to a species based on fin ray count (except caudal fin) because these numbers do not change with “growth.” Scales first appear on upper caudal lobe and/or along the lateral line. Head length and length of upper caudal lobe (except in “E.” hypsilepis) decrease relative to standard length during “growth.” Orbital length becomes shorter relative to head length i...

Diversity and size changes in palaeonisciform fishes (Actinopterygii, Pisces) from the Pennsylvanian Mazon Creek fauna, Illinois, U.S.A.

More than 25 kinds of fishes are known from the ironstone concretions which have yielded the Mazon Creek fauna. Included are unique soft bodied agnathans, several unusual chondrichthyans as well as acanthodians, crossopterygians, dipnoans and actinopterygii. A summary of the Mazon Creek fishes is presented with special emphasis on the paleoniscoids which are described and figured. Comparisons of Mazon Creek fishes with those of other Westphalian fish assemblages in Europe and North America show that the Illinois localities have produced the most diversified late Pennsylvanian fish fauna.

Fishes of the mazon creek fauna

The new albulid fish, Deltaichthys albuloides, is based on an almost complete specimen, which probably came from the Eagle Ford Shale (Upper Cretaceous) of Texas. The fossil is preserved in almost original shape, permitting description of much of the head skeleton. Possible reasons for the unusual preservation and the relationships of Deltaichthys to other albulids are discussed.

Deltaichthys albuloides, a new and unusually preserved albulid (Teleostei) probably from the Cretaceous of Texas

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