Abstract
The evolution of generic and species diversity in agnathans (orders Cyathaspidiformes and Pteraspidiformes) is analyzed. Cyathaspids appeared in the Silurian and achieved the peak of diversity in the first half of the Early Devonian (Lochkovian Stage and its analogues), as did pteraspids. Cyathaspids are absent from later beds. Pteraspids persisted to the end of the Early Devonian, although they sharply decreased in number in the second half of the Early Devonian (Pragian Stage and its analogues in Europe and America). Adaptive features of cyathaspids and pteraspids are considered. Some data on accompanying groups are discussed. It is proposed that these heterostracan orders became extinct mostly because of archaic locomotor adaptations and insufficient protection from predators. The insufficient protection primarily concerns juvenile cyathaspids. Cyathaspid and pteraspid genera included in the diagrams of changes in taxonomic diversity are listed.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
A. F. Abushik, “Silurian and Early Devonian Ostracodes of Podolia and Their Stratigraphical Significance,” in Proceedings of the 3rd International Symposium on the Silurian-Devonian Boundary and Biostratigraphy of the Silurian, Leningrad, 1968 (Nauka, Leningrad, 1971), Vol. 1, pp. 10–20 [in Russian].
Yu. G. Aleev and L. I. Novitskaya, “An Experimental Study of Hydrodynamic Features of Devonian Heterostracans,” Paleontol. Zh., No. 1, 3–12 (1983).
A. S. Alekseev, V. Yu. Dmitriev, and A. G. Ponomarenko, “Evolution of Taxonomic Diversity,” in Ecosystem Rearrangement and Evolution of the Biosphere (Geos, Moscow, 2001), Vol. 5, pp. 1–126 [in Russian].
A. Blieck, “Le genre Rhinopteraspis Jaekel (Vertébrés, Hétérostracés) du Dévonien inférieur: systématique, morphologie, répartition,” Bull. Mus. Nat. Hist. Natur., Sér. 4, Sect. C 2(1), 25–47 (1980).
A. Blieck, “Le genre Protopteraspis Leriche (Vertébrés, Hétérostracés) du Dévonien inférieur nord-atlantique,” Palaeontogr. A 173(5/6), 141–159 (1981).
A. Blieck, Les Hétérostracés Ptéraspidiformes, Agnathes du Silurien-Dévonien du continent nord-atlantique et des blocs avoisinants: Révision systématique, phylogénie, biostratigraphie, biogéographie (CNRS, Paris, 1984).
A. Blieck and N. Heintz, “The Cyathaspids of the Red Bay Group (Lower Devonian) of Spitsbergen: The Downtonian and Devonian Vertebrates of Spitsbergen: 13,” Polar Res., No. 1, 49–74 (1983).
A. Blieck, D. K. Elliott, and P.-Y. Gagnier, “Some Questions Concerning the Phylogenetic Relationships of Heterostracans: Ordovician to Devonian Jawless Vertebrates,” in Early Vertebrates and Related Problems of Evolutionary Biology, Ed. by M.-M. Chang et al. (Science Press, Beijing, 1991), pp. 1–17.
T. Bockelie and R. A. Fortey, “An Early Ordovician Vertebrate,” Nature 260(5546), 36–68 (1976).
R. H. Denison, “Early Devonian Fishes from Utah: 2. Heterostraci,” Fieldiana Geol. 11(7), 291–355 (1953).
R. H. Denison, “A Review of the Habitat of the Earliest Vertebrates,” Fieldiana Geol. 11(8), 359–457 (1956).
R. H. Denison, “New Silurian Heterostraci from Southeastern Yukon,” Fieldiana Geol. 14(7), 105–141 (1963).
R. H. Denison, “The Cyathaspididae a Family of Silurian and Devonian Jawless Vertebrates,” Fieldiana Geol. 13(5), 309–473 (1964).
R. H. Denison, “A New Protaspis from the Devonian of Utah, with Notes on the Classification of Pteraspididae,” Zool. J. Linn. Soc. London 47(311), 31–37 (1967).
R. H. Denison, “Revised Classification of Pteraspididae with Description of a New Form Wyoming,” Fieldiana Geol. 20(1), 1–41 (1970).
D. L. Dineley and E. J. Loeffler, “Ostracoderm Faunas of the Delorme and Associated Siluro-Devonian Formations N.W.T., Canada,” Spec. Pap. Palaeontol., No. 18, 1–214 (1976).
D. M. Drygant, “Conodont Zones in Analogues of the Ludlovian and Gedinnian Stages of Podolia,” in Proceedings of the 3rd International Symposium on the Silurian-Devonian Boundary and Biostratigraphy of the Silurian, Leningrad, 1968 (Nauka, Leningrad, 1971), Vol. 1, pp. 85–89 [in Russian].
D. K. Elliott and D. L. Dineley, “New Species of Protopteraspis (Agnatha, Heterostraci) from the Lower Devonian of Northwest Territories, Canada,” J. Paleontol. 56, 2 (1983).
D. K. Elliott, A. R. M. Blieck, and P.-Y. Gagnier, “Ordovician Vertebrates,” Geol. Surv. Canada, Spec. Pap., No. 90 (Advances in Ordovician Geology, Ed. by C. R. Barnes and S. H. Williams), 93–106 (1991).
P.-Y. Gagnier, “The Oldest Vertebrate: A 470-Million-Year-Old Jawless Fish, Sacabambaspis janvieri, from the Ordovician of Bolivia,” Nat. Geogr. Res. 5, 250–253 (1989).
P.-Y. Gagnier, A. R. M. Blieck, and G. Rodrigo, “First Ordovician Vertebrate from South America,” Geobios, No. 19, Part 5, 629–634 (1986).
J. Kiaer and A. Heintz, “The Downtonian and Devonian Vertebrates of Spitsbergen: 5. Suborder Cyathaspida: Part 1. Tribe Poraspidei, Family Poraspidae Kiaer,” Skr. Svalbard Ishavet. 40, 1–138 (1935).
B. K. Likharev, “Phylum Brahiopoda, General Part,” in Fundamentals of Paleontology: Bryozoans and Brachiopods, Ed. by T. G. Sarycheva (Akad. Nauk SSSR, Moscow, 1960), pp. 115–171 [in Russian].
T. Märss, “Structure of Tolypelepis from the Baltic Upper Silurian,” Izv. Akad. Nauk Eston. SSR, Khim., Geol. 26(1), 57–69 (1977).
L. I. Novitskaya, “The Earliest Agnathans of the USSR: Heterostracans: Cyathaspids, Amphiaspids, Pteraspids,” Tr. Paleontol. Inst. Akad. Nauk SSSR 219, 1–160 (1986).
L. I. Novitskaya, “On the Features of Contemporary Phylogenetic Research (Using the Problem of the Origin of Gnathostomes As an Example),” Paleontol. Zh., No. 6, 3–14 (2002) [Paleontol. J. 36 (6), 578–589 (2002)].
L. I. Novitskaya, “Subclass Heterostraci: Heterostracans,” in Agnathans and Ancient Fishes, Ed. by L. I. Novitskaya and O. B. Afanassieva (Geos, Moscow, 2004), pp. 69–207 [in Russian].
L. I. Novitskaya and V. N. Karatajute-Talimaa, “Ontogenetic Type As a Criterion for the Reconstruction of Phylogenetic Relationships of Lower Vertebrates,” Paleontol. Zh., No. 1, 3–16 (1989).
D. V. Obruchev, “Subclass Heterostraci (Pteraspides),” in Fundamentals of Paleontology: Agnathans and Fishes, Ed. by D. V. Obruchev (Akad. Nauk SSSR, Moscow, 1964), pp. 45–82 [in Russian].
D. V. Obruchev, “Significance of Vertebrates for Correlation of the Silurian and Lower Devonian Deposits of the USSR,” in Proceedings of the 3rd International Symposium on the Silurian-Devonian Boundary and Stratigraphy of the Lower and Middle Devonian, Leningrad, 1968 (Nauka, Leningrad, 1973), Vol. 2, pp. 189–197 [in Russian].
J. E. Repetski, “A Fish from the Upper Cambrian of North America,” Science 200(4341), 529–531 (1978).
A. Ritchie and J. Gilbert-Tomlinson, “First Ordovician Vertebrates from Southern Hemisphere,” Alcheringa 1(3), 351–368 (1977).
I. J. Sansom, M. P. Smith, M. M. Smith, and P. Turner, “The Harding Sandstone Revisited—A New Look at Some Old Bones,” Geobios, Mém. Spéc., No. 19, 57–60 (1995).
M. P. Smith and I. J. Sansom, “The Affinity of Anatolepis Bockelie et Fortey,” Geobios Mém. Spec., No. 19, 61–64 (1995).
L. B. Tarlo (Halstead), “Psammosteiformes (Agnatha)—A Review with Descriptions of New Material from the Lower Devonian of Poland: 2. Systematic Part,” Palaeontol. Polon., No. 15, 1–168 (1965).
V. K. Voichishin, “Armored Agnathans (Agnatha) of the Early Devonian of Podolia,” Candidate’s Dissertation in Biology (Gos. Prirod. Muz. Nats. Akad. Nauk Ukr., Lvov, 1998).
Author information
Authors and Affiliations
Additional information
Original Russian Text © L.I. Novitskaya, 2007, published in Paleontologicheskii Zhurnal, 2007, No. 3, pp. 33–46.
Rights and permissions
About this article
Cite this article
Novitskaya, L.I. Evolution of generic and species diversity in agnathans (Heterostraci: Orders Cyathaspidiformes, Pteraspidiformes). Paleontol. J. 41, 268–280 (2007). https://doi.org/10.1134/S0031030107030069
Received:
Issue Date:
DOI: https://doi.org/10.1134/S0031030107030069