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On the relationships of Psarolepis and the onychodontiform fishes
Journal of Verterbrate Paleontology
... Sarcopterygians (lobe-fi nned fi shes) are a successful group of bony fi shes (osteichthyans) with a long evolutionary history, from the middle Palaeozoic to the present day (Jarvik, 1980;Janvier, 1996;Long, 2001). The Sarcopterygii likely originated at the end of the Silurian (Zhu et al., 1999;Lu et al., 2017;Zhao et al., 2021) but diversifi ed during the Devonian (Ahlberg, 1991;Cloutier & Ahlberg, 1995, 1996, giving rise to various groups from which extant coelacanths, lungfi sh and tetrapods evolved (Janvier, 1996;Forey, 1998;Clack, 2012) (Fig. 1). ...
... However, numerous gaps in the fossil record from the early evolutionary history of non-tetrapod sarcopterygians makes the study of their origin and evolution challenging. One of the most ancient and enigmatic groups of extinct sarcopterygians are the onychodonts (Onychodontida or Onychodontiformes) (Jessen, 1967;Andrews, 1973;Andrews et al., 2006;Lu & Zhu, 2010;Lu et al., 2016;Mondéjar-Fernández, 2020), an exclusively Devonian group of predatory marine fi shes with "intermediate" characteristics between early osteichthyans and coelacanths (e.g., Long, 2001;Botella et al., 2007;Clement et al., 2018;Lu & Zhu, 2010;Lu et al., 2016;Lu et al., 2017;Zhu et al., 1999Zhu et al., , 2001Zhu et al., , 2006Zhu et al., , 2009Johanson et al., 2007;Mondéjar-Fernández, 2020). Currently, seven genera have been classified as Onychodontida: Onychodus Newberry, 1857;Strunius Jessen, 1966;Grossius Schultze, 1973;Luckeus Young & Schultze, 2005;Bukkanodus Johanson, Long, Talent, Janvier & Warren, 2007;Qingmenodus Lu & Zhu, 2010;and Selenodus Mondéjar-Fernández, 2020 (Fig. 2). ...
... Onychodonts are characterized by their complex and specialized cranial morphology, exemplified by the presence of hypertrophied sigmoid parasymphyseal teeth inserted onto paired whorls articulated on the symphysis of the dentaries with large palatal internasal pits in the floor of the ethmosphenoid complex to accommodate them (Andrews et al., 2006;Lu et al., 2016) (Fig. 2A, 2D). In addition, they have a highly kinetical intracranial joint, which gives a certain capacity for movement to the dermal bones of the skull (Long, 2001;Andrews et al., 2006). All currently described onychodonts lack cosmine on their dermal bones and scales, a remarkable histological feature that was basally present on the dermal skeleton of many other Palaeozoic sarcopterygians (Mondéjar-Fernández, 2020). ...
Onychodontida (Osteichthyes, Sarcopterygii) was an extinct group of Devonianpredatory marine fishes, representing an early branch in sarcopterygian evolution, andcurrently considered closely related to coelacanths (Actinistia). Due to their limited fossilrecord, the relationships of onychodonts within sarcopterygians, and whether all taxatraditionally considered as onychodonts form a clade, are still unclear. Here we review themost recent phylogenetic analyses by comparing their data matrices using recent toolsand methodology in quantitative comparative cladistics in order to evaluate the source ofdiscrepancies in the different datasets and provide possible practical solutions to test themonophyly of Onychodontida. These discrepancies range from the ambiguous formulationof character statements and character states to the poor preservation of certain fossils,which make interpretation of character states difficult. Understudied but highly completefossil specimens are also a source of missing data that have an impact in discording treetopologies. In-depth analysis and description of these specimens is needed to improvethe resolution of future phylogenetic analyses. Finally, we propose a formal stem-basedphylogenetic definition for Onychodontida.
... With the exception of the tetrapods, sarcopterygians have a long evolutionary history of diversity decline and are nowhere near as diverse today as they were at the beginning of their history. As a consequence, their early fossil record contains a number of groups that have proved more or less difficult to place in relation to the extant members, such as the onychodonts (1,2,5,6). ...
... Onychodonts are characterized by a distinctive head morphology that includes large parasymphysial tooth whorls with sigmoid teeth on their lower jaws and commensurately large internasal pits on the ethmoid floor to accommodate the whorls (6,12). In Onychodus, the ethmosphenoid region of the braincase has a series of distinctive features that all appear to form a functional complex with the strongly developed parasymphysial tooth whorls and internasal pits: notably, the vomers are absent, the parasphenoid is short, and the notochordal facet is extremely large (12). ...
... These genera combine onychodont-like ethmosphenoids, as well as lower jaws equipped with large parasymphysial tooth whorls, with primitive characteristics that suggest a placement in the sarcopterygian stem group or possibly the osteichthyan stem group (19,22,23). Some researchers have interpreted this character distribution as evidence that these early Chinese osteichthyans form a clade with onychodonts (6), but this conflicts with other characters such as the presence of a single humerus in Onychodus (and crown sarcopterygians) (12) but a multibasal pectoral fin in Psarolepis and Achoania (24). An alternative possibility is that the distinctive and seemingly specialized onychodont gestalt is, at least in part, primitive for the Sarcopterygii. ...
Crown or modern sarcopterygians (coelacanths, lungfishes, and tetrapods) differ substantially from stem sarcopterygians, such as Guiyu and Psarolepis, and a lack of transitional fossil taxa limits our understanding of the origin of the crown group. The Onychodontiformes, an enigmatic Devonian predatory fish group, seems to have characteristics of both stem and crown sarcopterygians but is difficult to place because of insufficient anatomical information. We describe the new skull material of Qingmenodus, a Pragian (~409-million-year-old) onychodont from China, using high-resolution computed tomography to image internal structures of the braincase. In addition to its remarkable similarities with stem sarcopterygians in the ethmosphenoid portion, Qingmenodus exhibits coelacanth-like neurocranial features in the otic region. A phylogenetic analysis based on a revised data set unambiguously assigns onychodonts to crown sarcopterygians as stem coelacanths. Qingmenodus thus bridges the morphological gap between stem sarcopterygians and coelacanths and helps to illuminate the early evolution and diversification of crown sarcopterygians.
... Jessen 1966: fig. 13;Long 2001), whereas the maxilla in this specimen is almost straight. A presumed suture runs back from the broken anterior edge to define its dorsal margin, indicating a long low element (Mx, Figure 39), perhaps most similar in shape to porolepiforms (e.g. ...
... The cheek unit of epe 37040 is difficult to interpret due to lack of information, and its affinities are uncertain, but the interpreted bone pattern ( Figure 42A) shows several interesting and unusual characteristics. The posterior extension of the tooth row on the maxilla is reminiscent of some onychodontids and actinopterygians, but in the former group the quadratojugal is missing (Jessen 1966;Long 2001). If the postorbital is correctly interpreted as a separate bone (?Po, Figure 39A), then the jugal sensory canal (a defining sarcopterygian feature according to Zhu and Schultze 2001) has a different course to that previously described, passing from the squamosal directly to the postorbital, rather than turning down G. C. Young, D. Goujet into the jugal. ...
... 14) and Psarolepis, which might therefore be primitive (Long 2001: 817). Direct comparison with the shoulder girdle of a Gogo 'OnycllOdus' (ANU V2976) shows that CPC 37045 is broader, with a more rounded posterior margin which lacks the sharp posterior angle, and has a less elongate ventral lamina than illustrated by Long (2001: fig. 1). ...
... New osteolepids of similar age from central Australia (Young & Schultze 2005) include the form Muranjilepis which shares characters with both Kenichthys, and Thursius wudinensis from China. The sister-group of 'osteolepiforms' in the consensus phylogeny (Fig. 2) is the rhizodontids, of which some of the earlier representatives (poorly known) come from East Gondwana , 2001Young et al. 1992, Young & Goujet 2003. The interpolation of rhizodontids above Kenichthys in the consensus phylogeny makes the osteolepiforms paraphyletic. ...
... Regarding the early history of some other poorly known lobe-finned fish groups (sarcopterygians), Long (2001) argued for a close relationship between the Siluro-Devonian Psarolepis from China (see Yu 1998), and the onychodontids, for which a long history in Australia is indicated by micro-remains, as well as the wealth of new morphological data from Gogo (Andrews et al. 2006), and skull bones and jaws of at least two new genera from the Early-Middle Devonian of Gondwana (Young & Schultze 2005, Johanson et al. in press). Psarolepis was first interpreted as a basal osteichthyan, then as a basal sarcopterygian (Basden et al. 2000, Basden & Young 2001. ...
... The relationships of the actinistians, represented by the living coelacanth Latimeria, is also subject to radically different opinions. They lie outside the two main subdivisions (dipnomorphs, tetrapodomorphs) in the consensus phylogeny (Fig. 2), but an alternative analysis places them closer to tetrapods (Zhu & Schultze 1997, 2001. Coelacanths have long been known from the Devonian, with the oldest unequivocal remains (from the Northern Hemisphere) of Givetian (late Middle Devonian) age (Friedman & Coates 2005). ...
Edited volume of conference papers from CAVEPS 2005. 475 pages.
... In crown sarcopterygians, the preopercular canal always has a horizontal portion (the jugal canal) extending forward to join the infraorbital canal within the jugal bone (Forey, 1998). The posteriorly expanded maxillary in broad contact with the preopercular is consistent with the condition in actinopterygians, and onychodont sarcopterygians (Long, 2001). Description An incomplete right flank scale is preserved, lacking the ventral part (Fig. 4). ...
Here we report a left cheek plate of Psarolepis, a postparietal shield of Youngolepis, a skull of Diabolepis, and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations (Lochkovian, Lower Devonian) of Nanning, Guangxi. This marks the first report of Diabolepis and Styloichthys beside Qujing, Yunnan, and the latest occurrence of Psarolepis to date. The fossil community displays significant similarities to the Xujiachong Assemblage, and provides new data for the Lower Devonian stratigraphic correlation between southwestern China and northern Vietnam. Given the latest dating constraint based on the conodont evidence, we regard that the Xujiachong Assemblage has a much longer range than previously supposed, extending from the latest Lochkovian to the end of Pragian. We propose that the transition of the Nahkaoling and Lianhuashan formations in Nanning might correspond to the Guijiatun Formation in Qujing. The relatively large size of fish individuals from Guangxi is probably attributed to the increase in the oxygen content of the ocean.
... The Gogo fish fauna is world-renowned for its high taxonomic diversity and spectacular three-dimensional preservation (Long 2006). Placoderm (Miles 1971), actinistian, acanthodian (Long and Trinajstic 2010), actinopterygian (Gardiner 1984), onychodontiform (Long 2001;Andrews et al. 2006), dipnoan (Miles 1977) and osteolepiform (Long 1985) taxa are known from Gogo, representing a fossil ichthyofauna with nearly 50 species described. ...
The modem Australian fauna includes one of the most enduring extant vertebrate lineages, the Dipnoi, and this body of work examines their anatomy, evolution and relationships, with insights from the Australian lungfish, Neoceratodus forsteri. Through application of modern technology and techniques, this thesis provides comparative, ontogenetic, phylogenetic and functional insights into both fossil and extant lungfishes. Three recently discovered fossil taxa are discussed. These include the first Gondwanan species of a European genus (Rhinodipterus kimberleyensis, Clement 2012), and a primitive genus belonging to the holodontid family (Xeradipterus hatcheri, Clement and Long 2010b), both from the Late Devonian Gogo Formation of Western Australia. Also, a Middle Devonian genus from central Australia (Harajicadipterus youngi, Clement 2009) and a detailed examination of the postcranial anatomy of two lungfishes from Victoria (Howidipterus donnae and Barwickia downunda, Long 1992a) is included. Key findings include the first unequivocal marine lungfish with air-breathing adaptations, possible examples ofsympatric speciation driven by competition for trophic resources, and some of the earliest dipnoans to make the transition to freshwater in Australia. Cladistic analysis was employed to examine dipnoan interrelationships, with special emphasis on early Australian forms. The analysis suggests there were significant adaptive radiations of lungfishes in Devonian reefs, with three locally-evolving clades identified; the chirodipterids, holodontids and dipnorhynchids. The monophyly ofa number ofgenera found in Australian deposits, namely Chirodipterus and Griphognathus is not supported, whereas, the monophyly of Rhinodipterus is confirmed. The analysis suggests that air-breathing probably evolved only once within the Dipnoi. Partition homogeneity tests and Farris' successive weighting provide support for the hypothesis that anatomical characters relating to feeding, such as those of the dentition, jaw and palate, may be less reliable than some other, less convergence-prone traits. Basic jaw lever mechanics in conjunction with 3D bite-modelling software were used to estimate bite force and velocity in extant and fossil genera. Neoceratodus was shown to have a mid level mechanical advantage for its bite compared to earlier fossil forms, implying it has neither a particularly strong nor fast bite. The two main adductor mandibulae muscle portions, the temporalis and masseter, contribute similar forces, and effective mechanical advantage remains constant throughout ontogeny despite an observable shift in diet. Analysis of functional morphology illustrates a large variety of feeding ecomorphologies, and thus, inferred behaviours of Devonian lungfishes. Early members of this lineage were evidently capable of eating diverse prey types, and likely filled a wide range of ecological roles. An inherent ability to remodel plastic dental morphologies is supported as a mechanism by which the early lungfishes were able to evolve, adapt and exploit new niches throughout their long history.
... (1) sister to the crown group Sarcopterygii (Friedman 2007); (2) as a plesion closely related to Psarolepis (Janvier 1996;Long 2001;Jeffery 2012); (3) sister to the rhipidistians (i.e. dipnomorphs and tetrapodomorphs; Cloutier & Ahlberg 1995 or to the rhipidistians excluding dipnoans (Schultze 1986;Long 1989;Young et al. 1992); and (4) sister group of the actinistians in an unnamed clade (Cloutier & Ahlberg 1995;Zhu & Schultze 1997Zhu et al. 1999Zhu et al. , 2006Zhu et al. , 2009Botella et al. 2007). ...
Onychodontids are a specialized and phylogenetically important group of marine sarcopterygians (lobe-finned fishes), probably closely related to coelacanths. However, they are among the least well-understood groups of early osteichthyans (bony fishes). The principal reason for this is their partly cartilaginous and therefore perishable endoskeleton, which causes the bones of the head to disarticulate and scatter after death.
A new onychodontid species from the Eifelian (Middle Devonian) of Morocco was found 40 years ago but it was only preliminarily described. These fossil remains can be attributed to a single individual and new preparation of the specimen has revealed new features and bones that were not previously known. Dermal skull bones are well preserved and allow a partially complete reconstruction of the snout, cheek and skull roof. Moreover, endoskeletal branchial and fin bones are exceptionally preserved, adding to our knowledge of early osteichthyan endoskeleton.
Preliminary phylogenetic placement supports its basal position among onychodontids, enabling to test evolutionary scenarios among the clade. This new species, along with well-preserved onychodontid fossils from Euramerica (Strunius from Germany) and Gondwana (Qingmenodus from China and specially Onychodus from Australia) adds to our knowledge of these elusive fishes. The Moroccan specimen, representing the first occurrence of onychodontids from Africa, constitute important material from a new Gondwanan locality that would furnish key information not only on onychodontid morphology and interrelationships, but also on their paleobiogeographical distribution and Devonian faunal affinities between Euramerica and Gondwana.
... Osorioichthys (184) Meemannia (46,185,186) Guiyu (1,187,188) Psarolepis (189)(190)(191)(192)(193)(194)(195)(196) Achoania (189,190,197) Onychodus (198)(199)(200) Miguashaia (201)(202)(203)(204) Styloichthys (190,205) Diabolepis (206,207) Youngolepis (208)(209)(210)(211)(212) Powichthys (213)(214)(215)(216) Porolepis (19,217,218) Glyptolepis (217,(219)(220)(221) Kenichthys (222,223) Osteolepis (19) Gogonasus (224)(225)(226)(227) Eusthenopteron (19) ...
A new sarcopterygian fish, Psarolepis, gen. nov. (Sarcopterygii, Osteichthyes) is described from the Lower Devonian of Eastern Yunnan, China. The new genus manifests many porolepiform-like features that are commonly used to distinguish porolepiforms from osteolepiforms, such as internasal cavity well developed, parasphenoid not protruding forward to ethmoidal region, vomeral area rectangular in shape and not meeting at median line, dorsal part of interorbital wall broad and tectum orbitale well developed, external surface of lower jaw with three large fossae, and well developed parasymphysial plates at anterior tip of lower jaws.This new form also shares some features with Powichthys, Youngolepis and Diabolepis that are not found in typical porolepiforms, such as intracranial joint situated at the level of the trigeminal exit, posterior face of ethmosphenoid facing posteroventrally, X-type skull table, and sutures always visible between premaxilla and the rest of the frontoethmoidal shield.Unique features of the new form include: complete lack of ventral or ventrolateral endoskeletal opening of the nasal cavity; extremely short sphenoidal region; presence of postorbital pillar flanking lateral cranial wall; supraorbital sensory canal not reaching anterior part of snout; median rostral toothed and taking part in upper jaw margin; and lower jaw with five coronoids.This new form probably represents a basal member of the clade that includes Powichthys, Youngolepis, Diabolepis and Dipnoi (=Dipnoiformes of Cloutier, 1990). The unusual character combination raises interesting questions about the interrelationship of the Dipnomorpha (sensu Ahlberg, 1991) and helps to illustrate the possible character transformation sequence of the stem lineage of dipnoans.
Living gnathostomes (jawed vertebrates) include chondrichthyans (sharks, rays and chimaeras) and osteichthyans or bony fishes. Living osteichthyans are divided into two lineages, namely actinopterygians (bichirs, sturgeons, gars, bowfins and teleosts) and sarcopterygians (coelacanths, lungfishes and tetrapods). It remains unclear how the two osteichthyan lineages acquired their respective characters and how their common osteichthyan ancestor arose from non-osteichthyan gnathostome groups. Here we present the first tentative reconstruction of a 400-million-year-old fossil ®sh from China (Fig. 1); this fossil fish combines features of sarcopterygians and actinopterygians and yet possesses large, paired fin spines previously found only in two extinct gnathostome groups (placoderms and acanthodians). This early bony fish provides amorphological link between osteichthyans and non-osteichthyan groups. It changes the polarity of many characters used at present in reconstructing osteichthyan interrelationships and offers new insights into the origin and evolution of osteichthyans.
The study of basal sarcopterygians is crucial to an understanding of the relationships and interrelationships of sarcopterygians, including their relationship to tetrapods. The new material from Qujing, Yunnan, southwestern China, represents the oldest known sarcopterygian fish and extends the record of sarcopterygians to the Late Silurian, or about 410 Ma. The new form is close to Youngolepis and Powichthys at the base of the Crossopterygii. Similarities among the lower jaws of onychodonts, porolepiforms, Youngolepis, Powichthys and the new form support a position of onychodonts within the Crossopterygii. Four characters in the character matrix of Cloutier & Ahlberg (1996, in Stiassny et al: Interrelationships of Fishes, Academic Press) are reviewed, and sarcopterygian interrelationships are studied on the basis of their data with minor modifications. The new scheme of sarcopterygian interrelationships differs markedly from Cloutier & Ahlberg's scheme. Neither actinistians nor onychodonts are situated at the base of Sarcopterygii, but within the Crossopterygii. Youngolepis and Powichthys are at the base of the Crossopterygii, instead of being the sister group of dipnoans plus Diabolepis.
Most living vertebrates, from teleosts to tetrapods, are osteichthyans (bony fishes), but the origin of this major group is poorly understood. The actinopterygians (ray-finned bony fishes) are the most successful living vertebrates in terms of diversity. They appear in the fossil record in the Late Silurian but are poorly known before the Late Devonian. Here we report the discovery of the oldest and most primitive actinopterygian-like osteichthyan braincase known, from 400-million-year-old limestone in southeastern Australia. This specimen displays previously unknown primitive conditions, in particular, an opening for a cartilaginous eyestalk. It provides an important and unique counterpart to the similarly aged and recently described Psarolepis from China and Vietnam. The contrasting features of these specimens, and the unusual anatomy of the new specimen in particular, provide new insights into anatomical conditions close to the evolutionary radiation of all modern osteichthyan groups.
The discovery of two Early Devonian osteichthyan (bony fish) fossils has challenged established ideas about the origin of osteichthyans and their divergence into actinopterygians (teleosts and their relatives) and sarcopterygians (tetrapods, coelacanths, lungfishes and related groups). Psarolepis from China and an unnamed braincase from Australia combine derived sarcopterygian and actinopterygian characters with primitive features previously restricted to non-osteichthyans, suggesting that early osteichthyan evolution may have involved substantial parallellism between sarcopterygians and actinopterygians. But interpretation of these fossils has been hampered by poor phylogenetic resolution. Here we describe a basal sarcopterygian fish, Achoania gen, et sp. nov., that fills the morphological gap between Psarolepis and higher sarcoptergyians. We also report the presence of eyestalk attachments in both Achoania and Psarolepis, showing that this supposedly non-osteichthyan feature occurs in basal sarcopterygians as well as the actinoptergyian-like Australian braincase.
In this field there has been an explosion of information generated by scientific research. One of the beneficiaries of this has been the study of morphology, where new techniques and analyses have led to insights into a wide range of topics. Advances in genetics, histology, microstructure, biomechanics and morphometrics have allowed researchers to view teeth from alternative perspectives. However, there has been little communication between researchers in the different fields of dental research. This book brings together overviews on a wide range of dental topics linking genes, molecules and developmental mechanisms within an evolutionary framework. Written by the leading experts in the field, this book will stimulate co-operative research in fields as diverse as paleontology, molecular biology, developmental biology and functional morphology.
Studies of the origin(1-3) and developmental genetics(4-7) of tetrapod limbs have focused attention on the need to identify the precise type of sarcopterygian (lobe-finned fish) hn from which limbs evolved. This can only be achieved through a phylogenetic analysis of sarcopterygians. Sarcopterygian fin skeletons vary in structures(8,9); use of an inappropriate fin skeleton as a model limb precursor will lead to erroneous inferences about the evolution of morphology and the developmental pathways at the fish-tetrapod transition. The pectoral fin of the rhizodont sarcopterygian Sauripteris is strikingly limb-like and features prominently in discussions about the origin of limbs(3,7,10-14). It is thus important to establish the phylogenetic position of rhizodonts. However, their anatomy is incompletely known(15,16). Published phylogenetic analyses are based on poorly substantiated characters, such as the alleged presence of two external nostrils in the Australian genus Barameda(17,18). Here we present, from the Upper Devonian period of Canowindra, Australia, the most primitive and by far the most complete rhizodont discovered so far. It has a single external nostril but possesses no other derived tetrapod-like features. Our new evidence shows that rhizodonts are more remote from tetrapods than are osteolepiform(18) and elpistostegid(19) lobe-fin fishes. Similarities between rhizodont fins and tetrapod limbs are thus probably convergent, and the pectoral fin of Sauripteris should not be used as a model limb precursor.
The anatomy of the axial skeleton, median fins and skull of the fossil group Porolepiformes (Osteichthyes: Sarcopterygii) is reviewed, and descriptions by previous authors are modified in the light of new evidence. The first dorsal fin support lacks radials, whereas the posterior radials in the second dorsal fin support form a branching structure. In the snout, porolepiforms primitively have two lateral rostral bones on each side, the posterior one corresponds to the “nariodal” of Jarvik, and the infraorbital canal runs along the suture between this bone and the premaxilla. A cladistic analysis based on 54 characters places the Porolepiformes as sister‐group of a clade Powichlhys + Youngolepis + Diabolepis + Dipnoi. The postcranial skeletons of porolepiforms and early lungfishes are very similar, and the skulls of Powichthys, Toungolepis and Diabolepis can be interpreted as forming a transformation series between porolepiform and dipnoan cranial morphologies. Lungfishes thus appear to be derived from ‘rhipidistian’ ancestors. The porolepiform‐lungfish clade is the sister group of another clade containing tetrapods, panderichthyids, osteolepiforms and rhizodonts. Onychodonts and coelacanths are joing unresolved sister groups of the other sarcopterygians. This cladogram is compared with those of other authors, and possible explanations for the differences are discussed. An outline classification of the Sarcopterygii is proposed.