Trimma annosum, Richard Winterbottom, 2003

Richard Winterbottom, 2003, A new species of the gobiid fish Trimma from the Western Pacific and Northern Indian Ocean coral reefs, with a description of its osteology., Zootaxa 218, pp. 1-24 : 2-19

Trimma annosum n. sp.

(Figs. 1 - 2).

Material examined

A total of 16 lots, 104 type specimens, plus numerous non-types from various localities.

Holotype: ROM 73126, 15.5 male, (ex ROM 40061), Fiji, Bau Waters, Cagilai Island off Ovalau Island, Viti Levu, P. Ryan and J. Brodie, 12 Apr. 1982.

Paratypes: China: NSMT - P55897, 1(21.1), Hainan Island, east coast of Xiaodonghai, G. Shinohara, 28 Nov 1997 . Fiji: ROM 40061, 5(11.8-17.4), collected with the holotype ; ROM 45968, 13(8.7-18.9), Kadavu, outer reef top on eastern side of Great Astrolabe Reef, due east of N tip of Dravuni, 6-10 m, collected by Winterbottom et al., 30 Mar 1983 ; ROM 45976, 13(9.9-17.9), Viti Levu, Suva Harbour at Rattail Pass, east side, 10-14 m, collected by Emery et al., 13 Apr 1983 ; ROM 990CS, 12(10.0-20.0), Viti Levu, Rattail Passage off Lamai, west side, 100 m from entrance, 0-2 m, collected by Emery et al., 19 Apr 1983 . Papua New Guinea: USNM 298774, 12(11.9-19.9), Ninigo Islands just SE of Ami Isl, patch reef (1º 14' S 144º 22' E), 0-4.6 m, V.G. Springer et al, 22 Oct 1978 . Philippines: ROM 49225, 2(16.2-20.9), Cebu, Bohol Strait, NW coast of Sumilon Island, between two sand beaches, 0-2 m, collected by Winterbottom et al., 11 Aug 1985 ; ROM 53149, 4(16.5-21.5), Negros Oriental, Siquijor Island, Mindanao Sea, Tonga Point, west side approx. 1 km from tip of point, coral head, 1- 3.7 m, collected by Johnson et al., 9 May 1987 ; ROM 53151, 14(9.5-16.5), Negros Oriental, Negros Island, Tanon Strait, mouth of Bais Bay, 3.0-5.2 m, collected by Winterbottom et al., 17 May 1987 . Solomon Islands: ROM 46041, 9(9.1-19.2), Guadalcanal, Honiara, 5 m, collected by Nichols et al., 12 Aug 1983 . Taiwan: RUSI 35452, 8(17.5-22.2), off Houpihu Kenting National Park, 22º 06'N 120º 45' E, collected by Heemstra and Shao, 20 Jan 1988 . Vietnam: ROM 73182, 1(15.2), Nha Trang Bay, Hon Mun Is, north side at midpoint of island, 0-3 m, 12º 10' 18.3" N 109º 18' 02.6"E, collected by Winterbottom et al., 21 May 2002 . ROM 73183, 5(19.1-22.7), Nha Trang Bay, SE side of Hon Mat Isl, 0-6 m, 12º 10' 37.4" N 109º 16' 43.5"E, collected by Winterbottom et al., 24 May 2002 . ROM 73184, 3(14.7-16.2), Nha Trang Bay, east side of Mun Isl, 0-7 m, 12º 10' 15.5"N 109º 18' 42.8"E, collected by Winterbottom et al, 26 May 2002 . ROM 73185, 1(19.0), Nha Trang Bay, SE side of Hon Mat Is, near rocky islets, 0-5 m, 12º 10' 30.8" N 109º 16' 40.2" E, collected by Winterbottom et al., 27 May 2002 .

Non-types: Australia (Coral Sea); WAM. China; ROM. Fiji; BPBM, ROM. India; FMNH. Indonesia; NTM. Maldives; FMNH. Micronesia; CAS. Palau; CAS. Papua New Guinea; CAS. Philippines; LACM, ROM. Solomon Islands; ROM.

Diagnosis

A species of Trimma with predorsal scales, a moderate interorbital trench (postorbital trench absent or poorly developed), second and third dorsal spines not elongate, a fifth pelvic fin ray which is branched dichotomously once and is 40-65% the length of the fourth (fifth pelvic fin ray is <50% of the fourth in 14% of the individuals examined). When alive, Trimma annosum is bluish grey with 3 or 4 rows of large yellow blotches on the head and body, with the uppermost row of blotches on each side of the dorsal fin joining medially to form saddles over the dorsum.

Description

The description is based on the holotype and up to 65 paratypes (values for the holotype in bold where appropriate). Dorsal fins VI + I 7-8 (mean = 7.9, n=31, 7 twice), second spine not elongate, reaching to the bases of the spine or first two rays of the second dorsal fin when adpressed, first ray of the second dorsal fin unbranched in all but two specimens examined (n= 31); anal fin I 7-8-9 (mean = 8.0, n=29), first ray unbranched; pectoral fin 17-18-19 (mean = 18.1, n=31), all rays unbranched, reaching posteriorly to a vertical in line with the anterior elements of the anal fin; pelvic fin I 5, no frenum, extent of basal membrane highly variable (10- 100% of the length of the fifth pelvic ray, but lower values may be the result of torn membranes), first four rays with a single sequential branch, fifth ray branching dichotomously once, 40-50-65% of the fourth ray (n=65, 9 specimens have fifth rays less than 50% of the fourth), fourth ray reaching posteriorly as far as the first few elements of the anal fin. Lateral scales 23-26-27 (mean = 24.6, n= 24, 27 once), anterior transverse scales 6-7-8 (mean = 7, n=24), posterior transverse scales 6-7 (mean = 7.0, n=24, 6 once); predorsal scales 5-6-7 (mean = 7, n=26); scales on breast cycloid, 3-4 cycloid scales on pectoral base, single ctenoid scale on opercle (often missing). Gill opening extending anteroventrally to below the posterior margin of the pupil to mid pupil. Teeth in lower jaw consist of an enlarged outer row of curved, spaced canines and an inner row of similar, but smaller canines with irregular rows of small conical teeth in between; outer row of teeth in the upper jaw similar to those of the lower jaw, with small irregular inner rows of teeth. Tongue truncate, gill rakers on first arch 2-3 + 10-11-12 = 12-15 (mean = 14.1, n=15). Anterior nasal opening a narrow tube, posterior nasal opening a large pore with a raised rim. Nasal openings are located on a raised oval sac located midway between the orbit and upper lip. Bony interorbital width 1/3-1/2 pupil width, with a moderate interorbital trench; postorbital trench poorly developed or absent; cephalic sensory papillae as in Fig. 2.

Colour pattern (from slides of freshly collected specimens from Fiji, Philippines, the Great Barrier Reef and Vietnam - see Fig. 1). Freshly collected specimens have 3-4 rows of yellow to orange spots on a dirty white to grey background. The rows of spots are loosely defined, and not vertically aligned, with the uppermost row close to the dorsal surface. Spots on caudal fin, and a row of spots just above the base or a basal stripe present on the dorsal fins, colour of paired fins yellow to orange. A single yellow-orange oval blotch (vertically oriented) is present on the pectoral base and two other such blotches occur on the upper and at the anteriormost portion of the opercle. A smaller spot, about half pupil diameter in width, is present immediately posterior to the eye and in line with the pupil. Cheek is uniform grey with no bars or spots. Scale pockets are strongly outlined with melanophores; a diffuse, yellow to orange ring around the pupil. Preserved (ethyl or isopropyl alcohol): background colour straw yellow with brown chromatophores. Scale pockets strongly outlined on head and anterior portion of body on some specimens. Cheek and snout uniformly dusky. First dorsal fin with a sprinkling of melanophores; second dorsal fin with two dark stripes, one basal, one in the middle of the fin; anal fin with a basal stripe and a second almost distal stripe. Pectoral fins often hyaline, but some specimens have melanophores along the fin rays. Some pigment is also present on the outer fin rays and membranes of the pelvic fins. Large light spots on head and body, six or seven large (pupil size) spots along the top 1/3 of the body. Four spots are immediately adjacent to the two dorsal fins, and two spots on the upper half of the caudal peduncle. These spots usually join at the dorsal surface to create a series of saddles. Second and third rows of spots not as distinct as uppermost row and often appear more like random blotches on the body. The four single spots seen on the opercle, pectoral base and behind the eye in freshly collected specimens are present in preserved material. A diffuse yellow ring is sometimes present around the pupil, and was particularly prominent in the specimens recently collected (May, 2002) in Vietnam.

Distribution

Trimma annosum is currently known from Bali, Papua New Guinea, Micronesia, Palau, China, Taiwan, Fiji, Philippines, Solomon Islands, Coral Sea and Vietnam. In addition, specimens which I identify as this species have also been collected at the Maldives and India in the northern Indian Ocean. Samples of this species have been collected between 0 and 14 m.

Comparisons

When alive, both Trimma annosum and Trimma DFH sp. 17 (an undescribed western Pacific species) share a pattern of yellow spots on a bluish-grey background. However Trimma DFH sp.17 has only two rows of very large squarish blotches, a large yellow blotch on the posterior half of the cheek, a naked predorsal and an unbranched fifth pelvic fin ray. In preserved material, the pattern on the body of Trimma DFH sp. 17 becomes one of thin irregular brown interconnected bars with a light spot on the cheek, while Trimma annosum retains a pattern of spots, particularly on the dorsal half of the body, and the entire cheek is dusky.

Freshly collected specimens of Trimma okinawae often have a pattern of large yellow to orange spots on the body, but can be distinguished from Trimma annosum by the presence of two vertically aligned light spots on the cheek (which may coalesce to form a bar) below the eye, an elongate second dorsal spine and branched pectoral-fin rays.

Etymology

From the Latin ‘ annosum’, full of years, long lived, aged; in allusion to the plain grey cheek of the new species, which is perhaps reminiscent of that class of elderly hirsute human males sometimes referred to as ‘ greybeards’. This species has been informally referred to as Trimma DFH sp. 9 . Suggested common name: greybearded pygmy goby.

Osteology of Trimma annosum

The osteology of Trimma is fairly typical of that of the Gobiidae in lacking nasal, suborbital(other than the lachrymal) and basisphenoid bones, and, as in all gobioids, also lacking the parietals. All bones are bilateral, except where noted otherwise.

Suspensorium (Figs. 3-5)

A small, ovoid, plate-like lachrymal is loosely attached to the anteroventrolateral margin of the lateral ethmoid, and overlaps the region of contact between the palatine and ectopterygoid. The premaxilla is a long flattened shaft of bone which curves anteriorly to join ligamentously with its antimere in the midline. The ventral margin bears an outer row of spaced, curved canine teeth which decrease gradually in size posteriorly; medial to this are several rows of short, straight, conical teeth irregularly arranged. A short ascending process arises from the posteromedial margin, its ventral surface strongly bound to the anterodorsal margin of an ovoid, median rostral cartilage. Immediately lateral to the ascending process is a broad, rounded articular process.

The maxilla is a laterally compressed shaft of bone with an anteroventrally directed deflection ventrally; its posterior one-third overlaps the posterodorsal margin of the premaxilla. The anterodorsal portion of the maxilla is formed by a complex head. The dorsomedial margin overlaps the lateral base of the articular process of the premaxilla. Beneath this, a curved process passes medially and anteriorly to support the ventral surface of the articular process and the anteroventromedial margin of the rostral cartilage. A well developed maxillo-ethmoid ligament passes posteromedially from the anterodorsolateral margin of the maxillary head to the anterior tip of the ethmoid.

The dentary is the largest of the lower jaw bones, and bears a short outer row of curved, enlarged, spaced canines from its symphysis to the bend of the lower jaw, a longer row of similar but smaller teeth in an inner row, and a few irregular rows of small conical teeth in between. The anguloarticular has an anterodorsal prong-like process which fits deeply into a concavity on the medial face of the dentary. It possesses a concave articular condyle which receives the convex head of the quadrate posterodorsally, and an anterior process on its medial surface to which the posterior margin of Meckel’ s cartilage attaches. The latter passes anteriorly into the median concavity (fossa) of the dentary, and is partially encased by a small coronomeckelian bone (visible but not labeled in Fig. 5) near its attachment to the anguloarticular. The retroarticular is plastered against the posteroventral corner of the anguloarticular, and is somewhat better developed on the medial than the lateral side. The palatine is a flattened shaft of bone which tapers posteroventrally along its contact with the ectopterygoid. It bears a complex anterodorsal head, with an anterolateral head ligamentously attached to the anterodorsal margin of the maxilla, and a medial head ligamentously attached to the anterolateral margin of the ethmoid. A strong ligament, the interpalatine ligament, passes medially and a little anteriorly to attach to the dorsal surface of the rostral cartilage and its antimere. In other gobiids, this ligament may attach to both its antimere and to the posterior tip of the ascending process of the premaxilla - e.g. Microgobius (see Birdsong, 1975).

The ectopterygoid is a flattened plate of bone which connects the posterior region of the palatine to the anterodorsal margin of the quadrate. The quadrate bears a double convex head which articulates with the posterodorsal margin of the anguloarticular anteroventrally; its anterodorsal margin slightly overlaps the posteroventral margin of the ectopterygoid. The dorsal surface is margined by cartilage. The posterodorsal margin is deeply indented, its medial surface being strongly attached to the lateral face of the anterior portion of the symplectic. The lateral surface of the well developed posterior flange is bound to the medial face of the horizontal limb of the preopercle, and loosely connected to the dorsomedial margin of the anterior region of the interopercle. There is a distinct notch in the ventral surface of the quadrate just posterior to its articular condyle with the anguloarticular. The symplectic is a strong, strut-like bone bound laterally to the quadrate anteriorly and the medial anteroventral face of the metapterygoid posterodorsally. Its posterior margin connects to the anterodorsal process of the hyomandibular through a plug of cartilage. There is no posteroventral process to the preopercle. The metapterygoid is a thin plate of bone bound to the lateral surface of the symplectic anteroventrally and the anterior rim of the hyomandibular posteriorly. The hyomandibular has a complex shape. Along its anterodorsal margin are two convex heads capped with cartilage for articulation with the cranium, the anterior fitting into a socket in the sphenotic, the posterior into a similar concavity in the pterotic. The posterior margin of the anterior head continues across the hyomandibular as a ridge to join the posterodorsal tip of the preopercle. A sharply angled process occupies the posterodorsal margin of the bone, below which is the articular condyle for the opercle. There is a large foramen for the passage of the seventh cranial nerve at about the middle of the hyomandibular, and its ventromedial margin bears a plug of cartilage between it and the medial face of the preopercle (and which continues dorsally between the hyomandibular and the symplectic). The preopercle is a flat, curved, roughly L-shaped bone with a thin lateral ridge running a little anterior to its posterior margin which fades out as it curves anteroventrally. It overlaps the posteroventral process of the quadrate anteriorly, as well as the dorsolateral margin of the interopercle along its more or less horizontal extent. The dorsomedial surface of the preopercle is bound to the ventrolateral margin of the hyomandibular, and there is a short anterodorsal process that projects towards (but does not contact) the posteroventral margin of the symplectic. The interopercle is a flattened, teretely oval bone with a membranous ventral margin. It tapers to a double point anteriorly, which is ligamentously connected to the retroarticular. Its dorsolateral surface is loosely joined to the ventromedial margin of the horizontal limb of the preopercle, and its rounded posterior margin is joined by a flat ligamentous band of tissue to the anteroventral tip of the subopercle. The subopercle is a flat, elongated, oval bone with a deep notch in its anterodorsal surface. The dorsal margin is strongly bound to the medial face of the posterior margin of the opercle by connective tissue. The opercle is a flat, rather triangular plate of bone with an articular process bearing a concave condyle for articulation with the hyomandibular on its anterodorsal apex.

Hyoid and Branchial Arches (Figs. 6-7)

The median basihyal is a broad spatulate bone tapering posteriorly, and is connected by ligamentous tissue to the dorso- and ventro-hyals. The former is a small bone that forms the anterodorsolateral margin of the hyoid arch, while the latter is somewhat better developed and forms the anterior margin of the arch. They are separated dorsally by a rounded plug of cartilage. The median urohyal is a vertical plate of bone with a rounded anterodorsal head which is firmly connected by a ligamentous sheath to the medial face of the dorsohyal, dorso-medial region of the ventrohyal, and the cartilaginous plug between them.

The anterior ceratohyal is the largest of the series, and is formed of a vertical plate of bone with the posterior one-third about three times the height of the anterior shaft. It bears a single, slim branchiostegal ray articulating with the ventral margin at about the middle of its length, and three much broader rays on the posterior one third of its ventrolateral margin. The posterior ceratohyal (a.k.a. epihyal) is a triangular bone with its apex posterodorsally. It supports the fifth branchiostegal ray on its ventrolateral margin. Posterodorsally, it articulates through a ligamentous sheath with a small interhyal which has a bulbous base and a rounded dorsal process that is firmly attached in the ventromedial cartilaginous region of the symplectic-hyomandibular junction.

The median basibranchials form the ventral margin of the branchial arches. The first, when present, is a minute nubbin of bone lying freely just anterior to the medial tips of the first hypobranchials.

The second basibranchial, a short, rod-like bone tapered anteriorly, lies between the posteromedial faces of the second hypobranchials anteriorly; its posterior face is firmly bound to the anterior face of the third basibranchial, which is a long rod of bone the posterior end of which lies between the medial faces of the third hypobranchials. The fourth basibranchial is a small round knob of cartilage. The three hypobranchials have a short anteriorly-directed process from their lateral margins, and are tipped with cartilage medially and posterolaterally where they join the anteroventral tips of the first three ceratobranchials. The first four ceratobranchials are long, curved, struts of bone tipped with cartilage. The first three attach ventrally to the posterolateral tips of the respective hypobranchials, the fourth is loosely joined to the posterolateral margin of the fourth basibranchial. The fifth ceratobranchial has a medially projecting shelf which bears numerous small conical teeth, and a rounded, ventrally projecting lamina on its ventral surface about one-quarter of the length of the bone at the base, and beginning at about the same distance from the anterior tip of the bone. The four epibranchials are short and rod-like, and tipped with cartilage. The first has a small medial uncinate process from its posterior surface at about the middle of its length to which is attached the lateral tip if the interarcual cartilage (a short round rod which attaches medially to the dorsolateral process of the second infrapharyngobranchial). The second epibranchial articulates with the lateralmost of the two anterodorsal processes of the third infrapharyngobranchial, the third, which bears a very short posterior uncinate process at the middle of its length, articulates with the posterolateral margin of that bone, and the fourth attaches to the third infrapharyngobranchial just behind it. No trace of a first infrapharyngobranchial was found. The second infrapharyngobranchial is a small, roughly triangular plate of bone with a tooth plate fused to its ventromedial surface. A short anterolateral process connects to the medial surface of the interarcual cartilage, and most of the bone is overlain dorsally by the paired anterolateral processes of the third infrapharyngobranchial. The third infrapharyngobranchial is a well developed flattened oval bone with an extensive toothplate fused to its ventral surface, and a broad anterolateral lamina overlying the second infrapharyngobranchial and which bears two small cartilage-tipped processes. The more lateral of these processes articulates with the posteromedial face of epibranchial 2 ventral to the latter’ s articulation with infrapharyngobranchial 2, while the more medial head is joined by a plug of cartilage to the anterodorsal rim of infrapharyngobranchial 2 medial to the latter’ s anterolateral process. A fourth toothplate is firmly affixed to the posterolateral margin of infrapharyngobranchial3, and is fully ossified with no trace of a fourth infrapharyngobranhial cartilage.

Cranium (Figs. 8-11)

The cranium of Trimma annosum is relatively streamlined and well ossified. The toothless, median vomer forms a squarish block at the anteroventral margin of the skull. It is connected to the mesethmoid dorsally by a large plug of cartilage, and to the lateral ethmoid posterolaterally. A short posterior process on the ventral surface lies in a groove in the dorsal surface of the anterior tip of the parasphenoid. The ventral profile of the vomer has a strong indentation, which marks the position of a horizontal crescentic shelf across the midline. The median mesethmoid lies between the lateral ethmoids laterally, and has a pair of lateral, dorsally-directed processes that embrace the anterior tips of the frontals. Posteriorly it forms a relatively extensive plate or septum in the anterior one-third of the orbit, attaching to the ventral surface of the frontals dorsally and the dorsal surface of the parasphenoid ventrally. The lateral ethmoid has a rather complex shape, with a triangular block anteroventrally and a vertical lateral plate of bone forming the anterior margin of the bony orbit posteriorly. The median parasphenoid forms a strut across the ventral margin of the orbit, which consists of a median, longitudinal ventral lamina and a pair of horizontal, lateral laminae. It broadens posteriorly to form the floor of the brain case, and contributes to the medial margin of the trigemino-fascialis foramen dorsolaterally.

The frontal is a large bone forming the anterodorsal roof of the braincase, tapering sharply to form a narrow strut across the dorsal rim of the orbit. The lateral margin of the strut slopes steeply towards the midline, to form a trough or trench between the orbits. The trough continues around the posterodorsal margin of the orbit, gradually fading out in the region of the dorsal margin of the sphenotic. The lateral margin of the posterior half of the frontal overlies the dorsal tip of the sphenotic, the posterolateral edge overlies the pterotic, and the posterior margin overlies the epioccipital (more laterally) and the supraoccipital (medially). The two frontals meet in the dorsal midline in an overlapping non-linear joint. The pterosphenoid (only visible in Fig. 11) is a small bone forming the wall of the anterior region of the brain case, joined to the frontal dorsally, the sphenotic laterally and the parasphenoid ventromedially. It forms the dorsal margin of the trigemino-fascialis foramen (which may be represented by two foramina).

The sphenotic forms the ventrolateral margin of the orbit, and has a complex shape. It meets the pterosphenoid in a vertical synchondral joint medially, underlies the frontals anterodorsally, and is connected to the pterotic posterodorsally through a plug of cartilage. Posteroventrally, it abuts the lateral margin of the pterotic, and is margined by the prootic ventromedially. The ventral surface of the lateral margin contains a well developed fossa which receives the anterior articular head of the hyomandibular. The pterotic forms the main lateral wall of the brain case. It is joined to the sphenotic anteriorly, the frontal dorsally, the epioccipital posterodorsally, the exoccipital posteriorly, basioccipital posteromedially, and the prootic anteromedially. Anterolaterally it bears a ventrally directed fossa for the articulation of the posterior head of the hyomandibular; behind this the lateral margin has a horizontal lateral flange. A roughly ovoid plate-like intercalar overlies the region of contact of the pterotic, prootic, basioccipital and exoccipital. Its posterolateral face provides an attachment site for the ligament connecting it to the ventral arm of the posttemporal. The occipital bones form the rear wall of the braincase. Dorsally, the median supraoccipital forms a wedge between the posteromedial margins of the frontals, and tapers posteriorly and ventrally. A supraoccipital crest begins anteriorly in the midline and becomes better developed posteriorly to form the posterodorsal profile of the cranium. Posterolaterally, the supraoccipital joins the dorsomedial margin of the epioccipital; its posterolateral margin is sutured to the medial margins of the exoccipitals. The posteroventral tip of the bone contributes marginally to the dorsal wall of the foramen magnum. The exoccipital forms the main portion of the ventrolateral wall of the brain case, has several nerve foramina on its lateral surface, and possesses a posteroventral condyle for the articulation of the first abdominal vertebra. It is sutured to the supraoccipital dorsomedially, the epioccipital dorsolaterally, the basioccipital anteromedially and the pterotic anteriorly. The anterolateral region is overlain by the intercalar. The median basioccipital, which forms the posteromedial floor of the braincase, is broad and deeply notched anteriorly, tapering posteriorly to end in a large, circular, centrum-like joint for articulations with the first abdominal vertebra. It is sutured to the exoccipital posterolaterally and the parasphenoid anteriorly, and has a synchondral joint with the prootic anterolaterally.

Pectoral girdle (Fig. 12)

The posttemporal, the dorsalmost element of the pectoral girdle, consists of a small, flat ovoid body with two long processes. The dorsal process passes anteriorly and medially, and attaches at its tip to the dorsal surface of the epioccipital. A more medial process passes anteroventromedially to end in a short ligament to the lateral surface of the intercalar. The posteromedial margin of the posttemporal is attached to the anterolateral surface of a flattened, rod-like supracleithrum, the medial surface of which is attached to, and overlies the deep notch in, the dorsal margin of the cleithrum. The cleithrum is the largest of the pectoral girdle bones. It is a vertically oriented, curved structure, with a lateral flange along its anterior margin, a posteroventral hook-like process, a ventromedial facet for the ventral intercleithral cartilage (figured but not labeled) and a larger, rounded, posteromedial flange from the posteroventral margin which articulates with the pelvic intercleithral cartilage. The posterior margin of the coracoid overlies the scapula dorsally and the cleithrum ventrally. These two bones are connected by a continuous sheet of cartilage.

The scapula is a small, somewhat square bone with a rounded indentation on its ventral margin which forms the dorsal portion of the scapula foramen. The foramen is bounded ventrally by the dorsal margin of the cartilaginous plate. The plate is attached to the medial face of the dorsal portion of the coracoid, which ends posteroventrally in a blunt process. There are four proximal pectoral radials, margined and separated by cartilage. The dorsalmost is small and triangular, the other three are rectangular structures which are thicker in the middle. The joint between the second and third radials expands to a larger ovoid space at about the middle of their lengths. The pectoral fin rays each embrace a small, round distal radial, and these articulate with the posterior cartilaginous rims of the proximal radials. A single curved sliver of bone, the postcleithrum (not figured), floats freely in the wall of the abdominal cavity posteromedial to the girdle.

Pelvic girdle (Fig. 13)

The anterior portion of the pelvic girdle consists of a large, sturdy pelvic intercleithral cartilage with a deep medial concavity. The anterior lateral surface is largely made up of the articular condyle which joins the girdle to the cleithra. Posteroventrally there is a well developed, rounded ventral process. The pelvic bone (paired) consists of a flattened plate which rises posterodorsally to form a domed structure in the dorsal midline. The lateral margin of the anterior portion of the bone possesses a longitudinal raised ridge. The posterolateral corner of the pelvis has a posterodorsally directed process with which the medial base of the pelvic spine articulates. The posterior margin supports a large, elongate cartilaginous block against which the pelvic fin rays articulate. A large gap is present between the medial faces of the anterior halves of the pelvic bones, which the dorsal pelvic processes partially overlie. The posterior edge of the dome has a short dorsal process projecting above the posteromedial margin of the girdle. The ventral face of the pelvic bone has a posteroventrolateral process which articulates with the pelvic spine, and a longitudinal sub-pelvic flange formed of a longitudinal ridge of bone immediately anterior to this. An anteroventrally, curved sub-pelvic process arises from the midline at about the middle of the length of the domed portion of the pelvic bone. The posteromedial tip is strongly bent ventrally to form a cup-shaped depression.

Vertebral column, dorsal and anal fins (Fig. 14)

There are ten abdominal vertebrae, all but the first two bearing a curved rib at the distal lateral surface of its parapophysis. The parapophyses increase in size from the seventh to tenth vertebrae. A series of 13 epineurals arise from the first 13 vertebrae. The first arises from the lateral face of the neural arch, the following epineurals arise from an increasingly ventral position as far as the last abdominal vertebra (where attachment is to the mid-region of the parapophysis). The 15 caudal vertebrae (plus the ural centrum - see below) are defined as those vertebrae posterior to the abdominal cavity in which the haemal arches meet in the ventral midline and extend ventrally as the haemal spine. The first caudal vertebra gives rise to its epipleural from the haemal arch, the second from the ventrolateral region of the centrum, and the third from the centrum a little below its midpoint. Foramina appear in the posterior half of the neural arches and tend to be larger posteriorly in the vertebral series, and may lose their dorsal margins.

The first dorsal fin is supported on six proximal/middle pterygiophores. Each bears a spine on its anterodorsal margin, and the second to fifth spines also contact the posterodorsal process of the pterygiophore immediately in front of it. The fifth pterygiophore lacks this process, and is separated by a distinct gap from the sixth pterygiophore and its spine. Two pterygiophores insert into the third interneural space, two in the next space, and one in each of the next two spaces, with no pterygiophore inserting into the seventh interneural space. This is represented as 3(2,2,1,1,0) in Birdsong’ s (1975) formula (subsequently modified to 3-22110). The first two pterygiophores of the second dorsal fin consist of a fused proximal/middle element and a small, rounded distal pterygiophore; the first pterygiophore bears the spine at its posterodorsal margin. The first fin ray of the second dorsal fin articulates with the second pterygiophore complex. Support for each of the remaining fin rays consists of a proximal, medial and distal pterygiophore, except the last ray where the distal pterygiophore is absent and the middle pterygiophore possesses an expanded posteroventral surface. The first anal proximal/middle pterygiophore has a short spine at its anteroventral margin, and its posteroventral process supports the anterior face of the first fin ray, the dorsal surface of which abuts on the ventral margin of the second proximal pterygiophore. The bases of both fin elements embrace a small rounded distal pterygiophore. The second and remaining pterygiophores consist of proximal, medial and distal entities as in the dorsal fin, with the last distal pterygiophore absent and has a posteroventrally expanded middle pterygiophore.

Caudal skeleton (Fig. 15)

All seven dorsal procurrent caudal fin rays (unbranched, unsegmented) are borne on the outer surface of the dorsal procurrent cartilage, which is attached ventrally to the dorsal margin of the epural posteriorly and the tips of the neural spines of the last two caudal vertebrae more anteriorly. The ventral procurrent cartilage bears the seven ventral procurrent rays, and is attached dorsally to the ventral margin of the haemal spine of the last caudal vertebra and anterodorsally to the tip of the preceding haemal spine. The last caudal vertebra(often referred to as pu2) has a slightly shorter neural spine than preceding vertebrae, but its haemal spine is very well developed with a large median flange arising from its anterior surface.

There is a single broad flat epural just posterior to the neural spine of pu2, its posteroventral border being rod-like. In some specimens (about 30%), there is a tiny separate piece of bone between it and the posterodorsal tip of the neural spine, but I am uncertain as to whether this represents the remnants of an independent separate epural or not. The dorsalmost of the principal caudal fin rays articulates with the posterodorsal tip of the rod-like portion of the epural. Immediately posterior to this, a small, splint-like fifth hypural bears the second unbranched segmented caudal fin ray. The ural centrum, a compound structure in origin, is completely fused to hypurals three and four, which form a triangular extension of the centrum, and which bears six (once seven, figured specimen) segmented, branched caudal fin rays along the posterior margin. Hypurals one and two are fused and represent the ventral counterpart of the upper hypural plate. The structure articulates anterodorsally in a deep fossa in the ventral surface of the ural centrum, and bears five segmented, branched caudal fin rays along its posterior margin. A short parhypural, the ventral counterpart of the fifth hypural, is well separated from the ural centrum, and bears the dorsalmost of the ventral unbranched, segmented caudal fin rays (the anteroventral two remaining such rays are borne on the ventral tip of the haemal spine of pu2).