Complexities of Early Teleostei and the Evolution of Particular Morphological Structures through Time
The subclass Teleostei Müller was erected in 1845 to contain all fishes possessing intermuscular bones (e.g., epineurals and epipleurals) and two arterial valves (in the conus arteriosus), and that are characterized also by the absence of muscles at the basal arteria (ventral aorta). Since these characters proved difficult for diagnosing fossils, the content of Teleostei was problematic from the start. These three characters are valid and uniquely derived, but the recognition of the taxon Teleostei sensu Müller has been ignored for most of the past 150 years, and the content of the group has changed numerous times. Additionally, a polyphyletic concept of Teleostei was the predominant idea for most of the last century. It was only during the 1970s that the monophyly of Teleostei was demonstrated. Although its monophyly is accepted, its content and phylogenetic relationships have been a subject of disagreement, with only some recent consensus between morphologists and molecular biologists. Understanding the history of Teleostei requires knowledge of its fossils forms. The monophyly of the total group Teleostei, which now includes Triassic pholidophorids, is supported by numerous synapomorphies, such as autosphenotic without small dermal component; unpaired vomer (in adults); complete ring of two sclerotic bones oriented anterior and posterior to orbit; and a hypural articulating with a few caudal rays—with further transformations in more advanced teleosts. Current evidence indicates that some Late Triassic taxa (†Pholidophoretes salvus and †Knerichthys bronni) from Europe represent the oldest known †pholidophorids, and the European genus †Prohalecites from the Ladinian/Carnian (Triassic; c. 240 Ma) boundary represents the oldest stem teleost. The synapomorphies now shared by living teleosts appeared stepwise more than 100 million years ago in the common ancestors of the sequential sisters of now living groups; they did not originate in the common ancestor of the three main living teleost clades (elopomorphs, and osteoglossomorphs plus clupeocephalans), and the analyses of character distribution reflects the gradual accumulation of features that now diagnose Recent teleosts. A list of characters supporting these hierarchical phylogenetic levels is provided.
Examples of teleosteomorphs or stem teleosts. (A) †Prohalecites porroi from the Middle Triassic of Varesse, northern Italy (MCSNIO P 348). Scale = 1 cm. (B) †Pachycormiform Orthocormus roeperi from the Upper Jurassic of Bavaria, Germany (BSPG 1993 XVIII‐VFKO B16). (C) †Aspidorhynchiform Aspidorhynchus acutirostris from the Upper Jurassic of Bavaria, Germany (BSPG 2012‐I‐1). Scales for B and C = 10 cm.
Examples of crown teleosts. (A) Elopomorph †Anaethalion sp. from the early Upper Jurassic of Bavaria, Germany (BSPG uncat.). (B) Stem ostariophysan †Tischlingerichthys viohli from the Upper Jurassic of Bavaria, Germany (JME Moe 8). (C) The stem euteleost †Leptolepides sp. from the early Upper Jurassic of Bavaria, Germany (JME ETT 249). Scales for A and C = 1 cm; B = 1 mm.
Johannes Müller, German anatomist who erected the class Teleostei in 1845. Photograph courtesy of Peter Bartsch (Berlin).
Intermuscular bones. (A) Epineural series of processes and vertebrae in the Early Jurassic teleost †Leptolepis coryphaenoides (BGHan 1956‐2, acid‐prepared specimen). Scale = 1 cm. (B) Series of anteriormost epineural processes in Elops saurus (CAS [SU] 10487). (C) Restoration of †Leptolepis coryphaenoides in lateral view. Note the series of epineural processes associated with the neural arches of the precaudal vertebrae (after Arratia, 1996). (D) Restoration of the Late Jurassic elopomorph †Anaethalion knorri in lateral view (after Arratia, 1996). Note the series of epineural processes associated with the neural arches of the precaudal vertebrae and the short series of small epipleural bones associated to the anteriormost caudal region. Abbreviations: epin.p, epineural processes; na, neural arches; ns, neural spines; sn, supraneurals; ona, accessory neural arch.
Phylogenetic hypothesis of major groups of teleosts (slightly modified from Arratia, 2001). Bold line identifies †Pholidophorus s. str. including †Ph. bechei (now = †Dorsetichthys bechei); Osteoglossocephala sensu Arratia (1999) and Betancur‐R. et al. (2013).
Diagrammatic representation of the phylogeny of Actinopterygii representing Teleostei (nr. 35) as a monophyletic group (slightly modified from Gross, 1964). Note that †Leptolepidae (nr. 35) is included at the base of the teleostean lineage and that †Pholidophoridae (nr. 34) as teleostean ancestor. 1, †Cheirolepidae;… 32, †Pachycormidae, 33, †Archaeomenidae; 34, †Pholidophoridae; 35, †Leptolepidae; 36, †Saurichthyidae; 37, †Pholidopleuridae; 38, †Ptycholepidae; … 44, †Pleuropholidae; 45, †Oligopleuridae; 46, †Aspidorhynchidae; 47, †Lepidotes; 48, Amia; 49, Lepisosteidae. For a complete list of taxa, see Gross (1964).
Hypotheses proposing a polyphyletic origin of teleosts (modified to facilitate comparisons). (A) Saint‐Seine (1949, 1956). (B) Nybelin (1961, 1964). (C) Greenwood et al. (1966).
Hypotheses proposing a monophyletic origin of teleosts (slightly modified to facilitate comparisons). (A) Patterson (1977a). (B) Arratia (1999). Extant teleostean lineages are shown in gray.
Hypothesis proposing a monophyletic origin of teleosts and the phylogenetic relationships among most primitive teleosts (after Arratia, 2013), excluding clupeocephalans. The extant teleostean lineages are shown in gray. Some of the synapomorphies supporting the main nodes are listed below; for a complete list, see Arratia (2013:114–118). Node A (total group teleost): autosphenotic without small dermal component; unpaired vomer (in adults); tube‐like canal bearing anterior arm of the antorbital absent; absence of two vertebral centra fused into occipital condyle; complete ring of two sclerotic bones oriented anterior and posterior to orbit; a hypural articulating with a few caudal rays; serrate appendages formed by a long, toothed element covering medial surface of cleithrum; accessory nasal sacs; craniotemporal muscle; heart with two arterial valves in conus arteriosus; and ventral aorta without muscles at its basal position. Node B: supraorbital and otic canals with simple tubules; ascending process of premaxilla present; mobile premaxilla present; moderately long maxilla reaching below the orbit; clavicle present; diplospondylous vertebrae in mid‐caudal region; and neural spine of preural centrum 1 present. Node C: one or two suborbital bones positioned ventrolateral to postorbital region of skull roof; two supramaxillary bones; articular bone fused with angular and retroarticular; “leptolepid” notch in the ascending margin of dentary; coronoid process of lower jaw formed by surangular; and one large dorsal scute preceding the caudal fin. Node D: elongate posteroventral process of quadrate present; symplectic not articulate with lower jaw; long epineural process of neural arch of abdominal vertebrae present; seven or more ural neural arches modified as uroneurals; and a diastema between hypurals 2 and 3. Node E: supraoccipital bone present; sutures between cartilage bones in braincase retained throughout life; symplectic medial to posterior margin of quadrate; each vertebral centra of caudal region of adult individuals formed by chordacentra surrounded by autocentra; and four pectoral radials present. Node F: posttemporal bone with a moderately small body and a distinct sharp process to articulate with cranium; coronoid bones absent in lower jaw; two hypohyals present; anterior serrated appendage absent; clavicle absent; two ural centra (in adults); and three or four epurals. Node G: skull roof with orbital region slightly narrower than postorbital region; prearticular bone absent; serrated appendage absent; and pectoral propterygium fused with base of 1st pectoral ray. Node H: foramen for glossopharyngeal nerve positioned in exoccipital; surangular bone absent; coronoid process formed by dentary and angular; tendon‐bone urohyal present; diplospondyly in midcaudal region absent; first and last principal caudal rays forming leading margin of caudal fin. Node I: incomplete ring of two sclerotic bones oriented anterior and posterior to eye; three or more postcleithra; pectoral and pelvic fins without fringing fulcra; 19 principal caudal rays; two tendon‐bone urodermals; homocercal caudal fin present; and cycloid type of scales. Node J: canals for occipital arteries in basioccipital absent; spiracular canal absent; suborbital bones absent; one supraorbital bone present; midcaudal autocentra thick and sculptured; notochord strongly constricted by the walls of autocentra; and epipleural intermuscular bones present (incorrectly listed as a synapomorphy of node E in Arratia, 2013); Node K: uroneurals inclined at different angles (as opposed to all uroneural inclined toward the horizontal, one after the other); caudal epaxial basal fulcra absent; and epaxial procurrent rays in close contact with epurals and uroneurals. Node L: foramen for vagus nerve placed in posterolateral face of the exoccipital alone; pectoral axillary process present; neural spines of preural centra 2 and 3 of similar length; and epaxial procurrent rays present. Node M: middle pit‐line groove short, not crossing the pterotic; “leptolepid” notch absent; many epipleural intermuscular bones present; pelvic axillary process formed by modified scales; five or less ural neural arches modified as uroneurals; and dorsal processes at the base of the principal caudal rays of the dorsal lobe absent.
Diagrammatic representation of the skull roof of certain actinopterygians illustrating differences between the preorbital and postorbital regions. (A) Non‐teleost Amia calva. (B) †Pholidophorid pattern. (C) †Leptolepis coryphaenoides. (D) Elops saurus. Abbreviations: asp, autosphenotic; dpt, dermopterotic; pa [=fr], parietal bone [=frontal of traditional terminology]; ppa [=pa], postparietal bone [=parietal of traditional terminology]; pt, pterotic; soc, supraoccipital.
Diagrammatic representation of some morphological structures in teleosts. (A) One supramaxilla (A) in the halecomorph Amia calva versus the teleostean condition of two supramaxillae (B) as represented by the †pholidophorid Pholidoctenus serianus (MCSNB 3377). (C) Lower jaw, part of suspensorium, and ceratohyal (†Pholidophorus gervasuttii; MCSNB 4302). (D) Quadrate (†Leptolepis coryphaenoides; SEM of specimen KUVP uncat.; 55X). Arrow in A points to the supramaxillary process, whereas arrow in C points to a small process in quadrate. Abbreviations: ang, angular; a.cer. anterior ceratohyal; ar+rar, articular fused with retroarticular; de, dentary; lat.ri, lateral ridge; l.no, “leptolepid” notch; mx, maxilla; mtg, metapterygoid; qu, quadrate; sang, surangular; smax, supramaxilla; sy, symplectic.
Part of the pectoral girdle of †pholidophorids illustrating the presence of a clavicle and a serrate appendage associated (identified by small arrows) with the cleithrum. (A) †Parapholidophorus nybelini (MCSNB 2962) oriented to the left. (B) †Pholidophorus gervasuttii (MCSNB 4304c) oriented to the left. Abbreviations: art.s, articular surface; b.pcl, broken dorsal postcleithrum; cl, cleithrum; clv, clavicle.
Diagrammatic caudal endoskeletons of some Late Jurassic teleosts illustrating differences in size, shape, and number of the same elements identified by colors. (A) †Prohalecites. (B) †Eurycormus. (C) †Ascalabos. (D) Elopomorph †Elopsomolos. (E) Ostariophysan †Tischlingerichthys. (F) Euteleost †Orthogonikleithrus. Abbreviations: chc, chordacentra; E1–5, epurals 1–5 (blue); H1–11, hypurals 1–11 (yellow); PH, parhypural; UN1–7, uroneurals 1–7 (reddish).
Types of caudal fins. Note differences in number and position of epurals (blue), uroneurals (reddish), hypurals (yellow), and principal fin rays forming the leading margins of the fins (gray). (A) Homocercal caudal fin represented by a reconstruction of the fin of the Late Jurassic euteleost †Orthogonikleithrus hoelli (based on JME ETT 2301 and 2632). (B) Hemiheterocercal caudal fin represented by a reconstruction of the fin of the Early Jurassic †Dorsetichthys bechei (based on MNHN 1870‐537B). Abbreviation: PR1–24, principal caudal‐fin rays 1–24.
Types of scales present in teleosts along its evolutionary history. Arrow indicates anterior. (A) Ganoid scale of lepisosteid type (†Pholidophorus latiusculus after Schultze, 1966). (B) Amioid type of scale (†Eurycormus speciosus; BSPG 1960 XVIII 106). (C) Cycloid type of scale (†Leptolepis coryphaenoides: BGHan i1957‐2).
Contributor Notes
Associate Editor: G. D. Johnson.