Holopterygius nudus Jessen (P 7789), latest Givetian–earliest Frasnian, Bergisch-Gladbach, Germany. ( a ) Photograph of P 7789a; ( b ) composite drawing based on P7789a-c; and ( c ) reconstruction. Bones outlined in grey in ( c ) were reconstructed based on Allenypterus . Scale bar represents 10 mm. Abbreviations: ano, anocleithrum; bp, basal plate of the second dorsal fin; chy, ceratohyal; cla, calvicle; cle, cleithrum; cop, principal coronoid; ex, extracleithrum; has, haemal arch and spine; gs, indeterminate components of the gill skeleton; nas, neural arch and spine; op, opercle; ot, otolith; pal, palate; pap, parapophyses; pmx, premaxilla; psph, parasphenoid; rd, radials of the dorsal lobe of the caudal fin; rv, radials of the ventral lobe of the caudal fin; sr, skull roof; sym, symplectic; vs, ventral keel scales. 

Contexts in source publication

Context 1

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 2

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 3

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 4

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 5

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 6

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 7

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 8

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 9

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 10

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 11

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 12

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 13

... a long tooth-bearing fragment on the opposite side of the skull probably represents a portion of the dentary from the other mandible. The deep dorsal process of the jaw is composed of an expanded posterior coronoid ( figure 1 b , cop), which is a coelacanth synapomorphy (Forey 1998). Small teeth anterior to the principal coronoid may be the remains of additional members of the series. The posterior ramus of the jaw corresponds to the retroarticular process of other coelacanths, and is overlain by a stocky cylindrical bone that is identified as the symplectic (figure 1 b , sym), a major component of the coelacanth tandem jaw joint. The ceratohyals (figure 1 b , chy) are flared distally and proximally. Narrow endoskeletal rods represent remains of the gill skeleton (figure 1 b , gs). The cleithrum and clavicles (figure 1 b , cle, cla) are well-preserved and exhibit the slender proportions characteristic of coelacanths crownward of Miguashaia (Cloutier 1996; Forey 1998). Holopterygius also possesses an extracleithrum (figure 1 b , ex), an additional dermal ossification that is a coelacanth synapomorphy (Forey 1998). Although Jessen (1973) noted the similarities between the pectoral girdles of Holopterygius and coelacanths, he did not consider this resemblance sufficient to justify placement within the group. Fragments of the anocleithrum (figure 1 b , ano) are located dorsal to the tip of the cleithrum, and suggest this bone was of the simple unbranched morphology primitive for actinistians. The distinctive postcranium of Holopterygius is leaf- shaped, with a greatly elongated caudal region. Despite the unusual body shape of this genus, the components of its postcranial skeleton conform to the general coelacanth pattern. There are approximately 80 postcranial segments, just over 20 of which are abdominal. Vertebral centra are unossified, but small ossifications located below the abdominal neural arches may represent parapophyses (figure 1 b , pap). There are no ossified ribs. Neural arches and spines (figure 1 b , nas) and haemal arches and spines (figure 1 b , has) are co-ossified. The dorsal and ventral lobes of the diphycercal caudal fin are each supported by a single row of endoskeletal radials (figure 1 b , rd, rv). There is a one-to-one ratio between radials and neural or haemal spines and a greater than one-to-one relationship between fin rays and radials. Jessen (1973) reconstructed Holopterygius with multiple radials per body segment, but this seems to have been informed by reference to conditions in tarrasiid actinopterygians (Lund & Melton 1982; Taverne 1996). Direct comparison with Tarrasius problematicus (Natural History Museum, London, P.1167, P.18064, P.18065, P.18061) confirms the difference in spine to radial ratios. It is not possible to determine whether the fin rays were segmented in Holopterygius as in most coelacanths, or unsegmented as in Allenypterus (Lund & Lund 1985). The dorsal and ventral lobes of the caudal fin are strongly asymmetrical, with the dorsal lobe extending much further anteriorly, as in Allenypterus (Lund & Lund 1985; Forey 1998). No components of the first dorsal, pectoral, anal or pelvic fins are preserved. An irregularly shaped ossification located dorsal to the neural spines immediately anterior to the first radial of the caudal fin probably represents the basal plate of the second dorsal fin (figure 1 b , bp). No squamation is preserved on the flanks of Holopterygius , but a series of keel scales run along the ventral margin of the body from just behind the skull to approximately the midpoint of the abdominal region (figure 1 b , vs). It is possible that the absence of scales covering the body of Holopterygius is size-related, as scales are often not preserved in small fossil coelacanths (Lund & Lund 1985). There is no indication of the ossified swim bladder characteristic of derived coelacanths. Widely cited studies place coelacanths as the most basal extant sarcopterygian radiation (Cloutier & Ahlberg 1996; Forey 1998), but little is known about their early history. While the first crown-group sarcopterygians are known from Lower Devonian (Lochkovian; 411–416 Ma) depos- its (Cloutier & Ahlberg 1996), the oldest unequivocal coelacanths are of Givetian age (385–392 Ma; Forey 1998; Long 1999; Forey et al . 2000). Previously described Devonian coelacanths fall into two morphological cat- egories: primitive forms ( Gavinia , Miguashaia ) with postcrania resembling those of other plesiomorphic sarcopterygians, and more crownward taxa ( Chagrinia , Diplocercides ) whose postcranial anatomy is similar to that of stratigraphically younger and phylogenetically more derived coelacanths, including the Recent Latimeria . Holopterygius marks a considerable anatomical departure from other Devonian forms, and a cladistic analysis places it as the sister taxon of Allenypterus , another early coelacanth with unusual postcranial morphology (analysis and results are described in figure 2 a ). Two unequivocal synapomorphies link these genera: a series of ventral keel scales and an asymmetrical caudal fin in which the dorsal lobe extends far beyond the anterior extremity of the ventral lobe. Both of these fishes have unstable taxonomic histories resulting from their unconventional body profiles; like Holopterygius , Allenypterus was identified as an actinopterygian (Melton 1969) before being recognized as a coelacanth (Lund & Lund 1984). Although Holopterygius and Allenypterus are unusual among coelacanths in having greatly elongated caudal regions, they are easily distinguished. While the deep body of Allenypterus is strongly arched dorsally and compara- tively straight ventrally, the postcranium of Holopterygius is shallower with more symmetrical dorsal and ventral margins. Small specimens of Allenypterus have a less exaggerated dorsal hump than larger individuals (Lund & Lund 1985; Field Museum, Chicago, PF10942, PF 10943a,b), but they retain greatly elongated neural spines above the abdominal region, unlike the short structures in Holopterygius . Both genera share asymmetrical lobes of the caudal fin, but the ventral lobe is more extensive in Holopterygius than in Allenypterus , where it is reduced to a minor series of shortened fin rays near the tip of the tail. Additional dissimilarities are present in the skulls. The premaxillae and mandibles of Allenypterus are edentulous (Lund & Lund 1985; Forey 1998) but bear well- developed teeth in Holopterygius . Additionally, lower jaw proportions of Holopterygius are unlike those of Allenypterus , but are similar to those of other early coelacanths (Lund & Lund 1985; Forey et al . 2000), suggesting that it had a more conventional skull shape than Allenypterus , in which the cranial region is drastically ...

Context 14

... probably precedes its first appearance (Harland et al . 1990). Therefore, the age of the fish beds is probably latest Givetian–earliest Frasnian ( ca 385 Ma; all dates in this article are from Gradstein et al . 2004). The skull roof of Holopterygius (figure 1 b , sr) is preserved primarily as an impression of its visceral surface, but intact areas are perforated by large, irregular pores for the supraorbital sensory canal. The premaxilla (figure 1 b , pmx) is squat and bears four large, irregularly shaped teeth. The dorsal surface of the splint-like parasphenoid (figure 1 b , psph) is exposed, and is marked by a well- developed hypophysial fossa. Much of the palate is visible (figure 1 b , pal), and it has the triangular shape characteristic of coelacanths (Forey 1998). The quadrate is preserved as a thickened region at the posteroventral corner of the palate, while a series of teeth along its ventral margin represent the remains of the ectopterygoid. A large, subspherical structure in the otic region is interpreted as an otolith (figure 1 b , ot; cf. Clack 1996). No dermal bones of the cheek can be identified. The opercle (figure 1 b , op) is a large rectangular bone with a long vertical axis, and resembles that of Allenypterus (Lund & Lund 1985; Forey 1998). The lower jaw of Holopterygius bears a long anterior ramus, a well-developed dorsal process at mid length, and another ramus posteriorly. The anterior arm of the lower jaw resembles the slender dentary of many early coelacanths (Lund & Lund 1985; Forey et al . 2000). Although the dentary of the intact jaw is preserved only as ...

Context 15

... probably precedes its first appearance (Harland et al . 1990). Therefore, the age of the fish beds is probably latest Givetian–earliest Frasnian ( ca 385 Ma; all dates in this article are from Gradstein et al . 2004). The skull roof of Holopterygius (figure 1 b , sr) is preserved primarily as an impression of its visceral surface, but intact areas are perforated by large, irregular pores for the supraorbital sensory canal. The premaxilla (figure 1 b , pmx) is squat and bears four large, irregularly shaped teeth. The dorsal surface of the splint-like parasphenoid (figure 1 b , psph) is exposed, and is marked by a well- developed hypophysial fossa. Much of the palate is visible (figure 1 b , pal), and it has the triangular shape characteristic of coelacanths (Forey 1998). The quadrate is preserved as a thickened region at the posteroventral corner of the palate, while a series of teeth along its ventral margin represent the remains of the ectopterygoid. A large, subspherical structure in the otic region is interpreted as an otolith (figure 1 b , ot; cf. Clack 1996). No dermal bones of the cheek can be identified. The opercle (figure 1 b , op) is a large rectangular bone with a long vertical axis, and resembles that of Allenypterus (Lund & Lund 1985; Forey 1998). The lower jaw of Holopterygius bears a long anterior ramus, a well-developed dorsal process at mid length, and another ramus posteriorly. The anterior arm of the lower jaw resembles the slender dentary of many early coelacanths (Lund & Lund 1985; Forey et al . 2000). Although the dentary of the intact jaw is preserved only as ...

Context 16

... probably precedes its first appearance (Harland et al . 1990). Therefore, the age of the fish beds is probably latest Givetian–earliest Frasnian ( ca 385 Ma; all dates in this article are from Gradstein et al . 2004). The skull roof of Holopterygius (figure 1 b , sr) is preserved primarily as an impression of its visceral surface, but intact areas are perforated by large, irregular pores for the supraorbital sensory canal. The premaxilla (figure 1 b , pmx) is squat and bears four large, irregularly shaped teeth. The dorsal surface of the splint-like parasphenoid (figure 1 b , psph) is exposed, and is marked by a well- developed hypophysial fossa. Much of the palate is visible (figure 1 b , pal), and it has the triangular shape characteristic of coelacanths (Forey 1998). The quadrate is preserved as a thickened region at the posteroventral corner of the palate, while a series of teeth along its ventral margin represent the remains of the ectopterygoid. A large, subspherical structure in the otic region is interpreted as an otolith (figure 1 b , ot; cf. Clack 1996). No dermal bones of the cheek can be identified. The opercle (figure 1 b , op) is a large rectangular bone with a long vertical axis, and resembles that of Allenypterus (Lund & Lund 1985; Forey 1998). The lower jaw of Holopterygius bears a long anterior ramus, a well-developed dorsal process at mid length, and another ramus posteriorly. The anterior arm of the lower jaw resembles the slender dentary of many early coelacanths (Lund & Lund 1985; Forey et al . 2000). Although the dentary of the intact jaw is preserved only as ...

Context 17

... probably precedes its first appearance (Harland et al . 1990). Therefore, the age of the fish beds is probably latest Givetian–earliest Frasnian ( ca 385 Ma; all dates in this article are from Gradstein et al . 2004). The skull roof of Holopterygius (figure 1 b , sr) is preserved primarily as an impression of its visceral surface, but intact areas are perforated by large, irregular pores for the supraorbital sensory canal. The premaxilla (figure 1 b , pmx) is squat and bears four large, irregularly shaped teeth. The dorsal surface of the splint-like parasphenoid (figure 1 b , psph) is exposed, and is marked by a well- developed hypophysial fossa. Much of the palate is visible (figure 1 b , pal), and it has the triangular shape characteristic of coelacanths (Forey 1998). The quadrate is preserved as a thickened region at the posteroventral corner of the palate, while a series of teeth along its ventral margin represent the remains of the ectopterygoid. A large, subspherical structure in the otic region is interpreted as an otolith (figure 1 b , ot; cf. Clack 1996). No dermal bones of the cheek can be identified. The opercle (figure 1 b , op) is a large rectangular bone with a long vertical axis, and resembles that of Allenypterus (Lund & Lund 1985; Forey 1998). The lower jaw of Holopterygius bears a long anterior ramus, a well-developed dorsal process at mid length, and another ramus posteriorly. The anterior arm of the lower jaw resembles the slender dentary of many early coelacanths (Lund & Lund 1985; Forey et al . 2000). Although the dentary of the intact jaw is preserved only as ...

Context 18

... probably precedes its first appearance (Harland et al . 1990). Therefore, the age of the fish beds is probably latest Givetian–earliest Frasnian ( ca 385 Ma; all dates in this article are from Gradstein et al . 2004). The skull roof of Holopterygius (figure 1 b , sr) is preserved primarily as an impression of its visceral surface, but intact areas are perforated by large, irregular pores for the supraorbital sensory canal. The premaxilla (figure 1 b , pmx) is squat and bears four large, irregularly shaped teeth. The dorsal surface of the splint-like parasphenoid (figure 1 b , psph) is exposed, and is marked by a well- developed hypophysial fossa. Much of the palate is visible (figure 1 b , pal), and it has the triangular shape characteristic of coelacanths (Forey 1998). The quadrate is preserved as a thickened region at the posteroventral corner of the palate, while a series of teeth along its ventral margin represent the remains of the ectopterygoid. A large, subspherical structure in the otic region is interpreted as an otolith (figure 1 b , ot; cf. Clack 1996). No dermal bones of the cheek can be identified. The opercle (figure 1 b , op) is a large rectangular bone with a long vertical axis, and resembles that of Allenypterus (Lund & Lund 1985; Forey 1998). The lower jaw of Holopterygius bears a long anterior ramus, a well-developed dorsal process at mid length, and another ramus posteriorly. The anterior arm of the lower jaw resembles the slender dentary of many early coelacanths (Lund & Lund 1985; Forey et al . 2000). Although the dentary of the intact jaw is preserved only as ...

Context 19

... probably precedes its first appearance (Harland et al . 1990). Therefore, the age of the fish beds is probably latest Givetian–earliest Frasnian ( ca 385 Ma; all dates in this article are from Gradstein et al . 2004). The skull roof of Holopterygius (figure 1 b , sr) is preserved primarily as an impression of its visceral surface, but intact areas are perforated by large, irregular pores for the supraorbital sensory canal. The premaxilla (figure 1 b , pmx) is squat and bears four large, irregularly shaped teeth. The dorsal surface of the splint-like parasphenoid (figure 1 b , psph) is exposed, and is marked by a well- developed hypophysial fossa. Much of the palate is visible (figure 1 b , pal), and it has the triangular shape characteristic of coelacanths (Forey 1998). The quadrate is preserved as a thickened region at the posteroventral corner of the palate, while a series of teeth along its ventral margin represent the remains of the ectopterygoid. A large, subspherical structure in the otic region is interpreted as an otolith (figure 1 b , ot; cf. Clack 1996). No dermal bones of the cheek can be identified. The opercle (figure 1 b , op) is a large rectangular bone with a long vertical axis, and resembles that of Allenypterus (Lund & Lund 1985; Forey 1998). The lower jaw of Holopterygius bears a long anterior ramus, a well-developed dorsal process at mid length, and another ramus posteriorly. The anterior arm of the lower jaw resembles the slender dentary of many early coelacanths (Lund & Lund 1985; Forey et al . 2000). Although the dentary of the intact jaw is preserved only as ...