Jürgen Kriwet

Molecular systematics and global phylogeography of angel sharks (genus Squatina)

Angel sharks of the genus Squatina represent a group comprising 22 extant benthic species inhabiting continental shelves and upper slopes. In the present study, a comprehensive phylogenetic reconstruction of 17 Squatina species based on two mitochondrial markers (COI and 16S rRNA) is provided. The phylogenetic reconstructions are used to test biogeographic patterns. In addition, a molecular clock analysis is conducted to estimate divergence times of the emerged clades. All analyses show Squatina to be monophyletic. Four geographic clades are recognized, of which the Europe-North Africa-Asia clade is probably a result of the Tethys Sea closure. A second sister group relationship emerged in the analyses, including S. californica (eastern North Pacific) and S. dumeril (western North Atlantic), probably related to the rise of the Panamanian isthmus. The molecular clock analysis show that both lineage divergences coincide with the estimated time of these two geological events.

Molecular phylogeny and node time estimation of bioluminescent Lantern Sharks (Elasmobranchii: Etmopteridae).

Deep-sea Lantern Sharks (Etmopteridae) represent the most speciose family within Dogfish Sharks (Squaliformes). We compiled an extensive DNA dataset to estimate the first molecular phylogeny of the family and to provide node age estimates for the origin and diversification for this enigmatic group. Phylogenetic inferences yielded consistent and well supported hypotheses based on 4685bp of both nuclear (RAG1) and mitochondrial genes (COI, 12S-partial 16S, tRNAVal and tRNAPhe). The monophyletic family Etmopteridae originated in the early Paleocene around the C/T boundary, and split further into four morphologically distinct lineages supporting three of the four extant genera. The exception is Etmopterus which is paraphyletic with respect to Miroscyllium. Subsequent rapid radiation within Etmopterus in the Oligocene/early Miocene was accompanied by divergent evolution of bioluminescent flank markings which morphologically characterize the four lineages. Higher squaliform interrelationships could not be satisfactorily identified, but convergent evolution of bioluminescence in Dalatiidae and Etmopteridae is supported.

Permian–Triassic Osteichthyes (bony fishes): diversity dynamics and body size evolution

The Permian and Triassic were key time intervals in the history of life on Earth. Both periods are marked by a series of biotic crises including the most catastrophic of such events, the end‐Permian mass extinction, which eventually led to a major turnover from typical Palaeozoic faunas and floras to those that are emblematic for the Mesozoic and Cenozoic. Here we review patterns in Permian–Triassic bony fishes, a group whose evolutionary dynamics are understudied. Based on data from primary literature, we analyse changes in their taxonomic diversity and body size (as a proxy for trophic position) and explore their response to Permian–Triassic events. Diversity and body size are investigated separately for different groups of Osteichthyes (Dipnoi, Actinistia, ‘Palaeopterygii’, ‘Subholostei’, Holostei, Teleosteomorpha), within the marine and freshwater realms and on a global scale (total diversity) as well as across palaeolatitudinal belts. Diversity is also measured for different palaeogeographical provinces. Our results suggest a general trend from low osteichthyan diversity in the Permian to higher levels in the Triassic. Diversity dynamics in the Permian are marked by a decline in freshwater taxa during the Cisuralian. An extinction event during the end‐Guadalupian crisis is not evident from our data, but ‘palaeopterygians’ experienced a significant body size increase across the Guadalupian–Lopingian boundary and these fishes upheld their position as large, top predators from the Late Permian to the Late Triassic. Elevated turnover rates are documented at the Permian–Triassic boundary, and two distinct diversification events are noted in the wake of this biotic crisis, a first one during the Early Triassic (dipnoans, actinistians, ‘palaeopterygians’, ‘subholosteans’) and a second one during the Middle Triassic (‘subholosteans’, neopterygians). The origination of new, small taxa predominantly among these groups during the Middle Triassic event caused a significant reduction in osteichthyan body size. Neopterygii, the clade that encompasses the vast majority of extant fishes, underwent another diversification phase in the Late Triassic. The Triassic radiation of Osteichthyes, predominantly of Actinopterygii, which only occurred after severe extinctions among Chondrichthyes during the Middle–Late Permian, resulted in a profound change within global fish communities, from chondrichthyan‐rich faunas of the Permo‐Carboniferous to typical Mesozoic and Cenozoic associations dominated by actinopterygians. This turnover was not sudden but followed a stepwise pattern, with leaps during extinction events.

Additions to the Eocene selachian fauna of Antarctica with comments on Antarctic selachian diversity

Abstract Antarctic Eocene selachians were reported from the La Meseta Formation of Seymour Island and from glacial erratics of Mount Discovery, Antarctica. Seymour Island has produced the most diverse Palaeogene selachian fauna of the Southern Hemisphere so far. Up to now, 23 selachian taxa (20 sharks, 2 rays) have been described from the Eocene of Antarctica. Recent geological and palaeontological investigations on Seymour Island yielded new selachian remains from Lutetian (middle Eocene) deposits. An upper tooth is referred to the requiem shark Carcharhinus and a rostral spine to the sawfish Pristis. These occurrences represent the first Eocene records of both groups in the Southern Hemisphere and extend their geographic distribution. In addition, a fragmentary stinging ray attributed to Myliobatoidea is presented for the first time from Antarctica. The diversity of Eocene La Meseta fishes is reflected.

Cryptic diversity and species assignment of large lantern sharks of the Etmopterus spinax clade from the Southern Hemisphere (Squaliformes, Etmopteridae)

Straube, N., Kriwet, J. & Schliewen, U. K. (2010). Cryptic diversity and species assignment of large lantern sharks of the Etmopterus spinax clade from the Southern Hemisphere (Squaliformes, Etmopteridae). —Zoologica Scripta, 40, 61–75.

Timing of deep-sea adaptation in dogfish sharks: insights from a supertree of extinct and extant taxa

Klug, S. & Kriwet, J. (2010). Timing of deep‐sea adaptation in dogfish sharks: insights from a supertree of extinct and extant taxa. —Zoologica Scripta, 39, 331–342.

Ultimate Eocene (Priabonian) chondrichthyans (Holocephali, Elasmobranchii) of Antarctica

ABSTRACT The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of Squalus, Squatina, Pristiophorus, Striatolamia, Palaeohypotodus, Carcharocles, and Ischyodus from the upper parts of TELM 7 (Priabonian), including the first record of Carcharocles sokolovi from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene—Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics.

Egg capsule morphology provides new information about the interrelationships of chondrichthyan fishes

Chondrichthyan egg capsules have been well known since the nineteenth century, although their systematic affinities have been controversial for much of this time. Currently, 10 chondrichthyan egg capsule morphotypes are distinguished but their phylogenetic signal and evolutionary traits have not yet been analysed. Here, we present an analysis of all extant and currently known fossil chondrichthyan egg capsule types, and use a purported placoderm egg capsule as an outgroup for character coding. The phylogenetic hypothesis based on discrete morphological characters indicates that the enigmatic Carboniferous egg capsule morphotypes Crookallia and Vetacapsula form a monophyletic group together with the egg capsule morphotype of chimaerid holocephalans. The elasmobranch egg capsule morphotypes are sister to the holocephalan types. Based on these results we conclude that the ancestral chondrichthyan egg capsule morphotype combined features of those found in callorhinchid holocephalans and placoderms. From this ancestral type, two lineages of chondrichthyan egg capsule morphotypes diverged leading towards the major modern egg capsule morphotypes.

Before the freeze: otoliths from the Eocene of Seymour Island, Antarctica, reveal dominance of gadiform fishes (Teleostei)

The first record of fossil teleostean otoliths from Antarctica is reported. The fossils were obtained from late Early Eocene shell beds of the La Meseta Formation, Seymour Island that represent the last temperate marine climate phase in Antarctica prior to the onset of cooling and subsequent glaciation during the late Eocene. A total of 17 otolith-based teleost taxa are recognized, with 10 being identifiable to species level containing nine new species and one new genus: Argentina antarctica sp. nov., Diaphus? marambionis sp. nov., Macruronus eastmani sp. nov., Coelorinchus balushkini sp. nov., Coelorinchus nordenskjoeldi sp. nov., Palimphemus seymourensis sp. nov., Hoplobrotula? antipoda sp. nov., Notoberyx cionei gen. et sp. nov. and Cepola anderssoni sp. nov. Macruronus eastmani sp. nov. is also known from the late Eocene of Southern Australia, and Tripterophycis immutatus Schwarzhans, widespread in the southern oceans during the Eocene, has been recorded from New Zealand, southern Australia, and now Antarctica. The otolith assemblage shows a typical composition of temperate fishes dominated by gadiforms, very similar at genus and family levels to associations known from middle Eocene strata of New Zealand and the late Eocene of southern Australia, but also to the temperate Northern Hemisphere associations from the Paleocene of Denmark. The Seymour Island fauna bridges a gap in the record of global temperate marine teleost faunas during the early Eocene climate maximum. The dominant gadiforms are interpreted as the main temperate faunal component, as in the Paleocene of Denmark. Here they are represented by the families Moridae, Merlucciidae (Macruroninae), Macrouridae and Gadidae. Nowadays Gadidae are a chiefly Northern Hemisphere temperate family. Moridae, Macruroninae and Macrouridae live today on the lower shelf to deep-water or mesopelagically with Macruroninae being restricted to the Southern Ocean. The extant endemic Antarctic gadiform family Muraenolepididae is missing, as are the dominant modern Antarctic fishes of the perciform suborder Notothenioidei. Recently, there has been much debate on isolated jaw bones of teleost fishes found in the La Meseta Formation and whether they would represent gadiforms (Merlucciidae in this case) or some early, primitive notothenioid. Otoliths are known to often complement rather than duplicate skeletal finds. With this in mind, we conclude that our otolith data support the presence of gadiforms in the early Eocene of Antarctica while it does not rule out the presence of notothenioids at the same time. http://zoobank.org/urn:lsid:zoobank.org:pub:A30E5364-0003-4467-B902-43A41AD456CC

A NEW PYCNODONT FISH GENUS (NEOPTERYGII: PYCNODONTIFORMES) FROM THE CENOMANIAN (UPPER CRETACEOUS) OF MOUNT LEBANON

Abstract A new taxon of pycnodont fishes, Hensodon, is described on the basis of a well-preserved and articulated skeleton from the Cenomanian limestones of Hakel, Lebanon. A single species, Hensodon spinosus (Hennig, 1907), is assigned to the new genus. Hensodon is placed within Coccodontidae and is sister to Trewavasia. Features of Hensodon are: three massive, paired parietal and postparietal spines; a well-developed dorsal prominence rising to a high and distinct spinose apex, with the leading edge being straight and covered by a series of nuchal plates; two styliform dentalosplenial teeth and knoblike molariform prearticular and vomerine teeth; styliform branchial teeth; peltate squamation with only eight scale rows; and pelvic and anal fins preceded by strong and accentuated spines. The similar pycnodont Trewavasia differs in the presence of a single paired parietal spine, dorsal prominence without apical spines, loricate squamation pattern, scales with horizontal keels ending in a posterior spine, a dermal plate on the anterior ventral body part, no ventral apex, and a considerably higher number of hypurals. The phylogeny of pycnodonts is discussed and the paleobiogeographic patterns of Lebanese pycnodonts are reviewed.