Mataichthys Schwarzhans, Scofield, Tennyson, and T. Worthy

Schwarzhans, Werner, Scofield, R. Paul, Tennyson, Alan J. D., Worthy, Jennifer P. & Worthy, Trevor H., 2012, Fish remains, mostly otoliths, from the non-marine early Miocene of Otago, New Zealand, Acta Palaeontologica Polonica 57 (2), pp. 319-350 : 334-339

Genus Mataichthys Schwarzhans, Scofield, Tennyson, and T. Worthy nov.

Type species: Mataichthys bictenatus Schwarzhans, Scofield, Tennyson, and T. Worthy sp. nov.; see below.

Etymology: After Mata Creek and the fish−rich rocks therein, where the holotype was found: “mata”, as a noun in Maori can refer to a receptacle packed with preserved fish or birds, or a rock or stone, among other things (Williams 1971). Gender masculine.

Diagnosis.—An extinct genus of the family Eleotridae with the following combination of characters: body depth at ventral fin base about 16% SL; total vertebrae 28 (12 precaudal, 16 caudal); dorsal fin rays VI in first dorsal and I+ 10 in second dorsal; ventral fins separate, with I+7 rays; anal fin rays I+6 or 7, origin under 13 th vertebra and under 4 th ray of D2; caudal skeleton with 3 separated epurals; ctenoid body scales with alternating primary and secondary short and stout peripheral cteni of equal length; otoliths with median sulcus, pronounced postventral and variably developed anterior−ventral projections.

Species included.— Mataichthys comprises one species based on a skeleton find with otoliths in situ and many isolated otoliths of the same species, namely M. bictenatus and three more otolith−based species allocated purely on otolith correlation ( M. procerus , M. rhinoceros , and M. taurinus ) all from the early Miocene of the Bannockburn Formation, Otago, New Zealand.

Comparisons.—The separation of the ventral fins in the fossil skeleton suggests assignment of Mataichthys to Eleotridae (ventral fins are fused in Gobiidae , separate in Eleotridae ) and this is further supported by characters of the caudal skeleton and the otoliths. Amongst Eleotridae , the extant Gobiomorphus and Philypnodon are considered related genera by Hoese and Gill (1993), although Thacker and Hardman (2005) do not interpret them as closely related. Both genera, however, are endemic to New Zealand and temperate Australia and are found in freshwater and marginal marine environments (diadromous). The high total number of vertebrae (27–29 in Gobiomorphus and Philypnodon ), the anal fin origin far behind D2 origin (under 4 th to 5 th ray of D 2 in Gobiomorphus and Philypnodon ) and the general structure of the otolith (groups with Gobiomorphus and Philypnodon , see above) are shared features.

The specific organization of the caudal skeleton with its three broad, narowly separated epurals is closest to the structure observed in Gobiomorphus , but there the 2 nd and 3 rd epurals are fused or nearly fused, whereas in Mataichthys all three epurals are separate. In Butis and Philypnodon all epurals are fused. Bostrychus (see Winterbottom 1993) has three narrow epurals of which the 2 nd and 3 rd are fused at the base. Ophiocara and Ophieleotris have only two narrow and separate epurals. For detailed figures see Fig. 9 and Hoese and Gill (1993) on eleotrid phylogeny.

Another character separating Mataichthys from Gobiomorphus (and Philypnodon ) is the low number of anal fin rays (I+6 or 7 versus I+8–10). Few eleotrids have such low counts (i.e., Ophiocara ). However, the skeleton of the type specimen of Mataichthys bictenatus Schwarzhans, Scofield, Tennyson, and T. Worthy sp. nov. (see below) is not well enough preserved in this region to be certain. The number of ventral fin rays (I+7) is higher than in Gobiomorphus and Philypnodon (I+5–6).

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As in Gobiomorphus species the scales of Mataichthys bictenatus are peripherally ctenoid ornamented ( Roberts 1993). They differ in that the single row of cteni have alternating primary and secondary peripheral short and stout cteni of equal length ( Fig. 10 ), which are inserted in two bands at an upper and lower level with their bases overlapping. Scales of Gobiomorphus species ( Roberts 1993; McDowall et al. 2006b) show a single row of primary cteni ( Fig. 10 ). The only record of alternating primary and secondary cteni among Recent eleotrids has been reported in Eleotris by Roberts, though many more eleotrid genera have yet to be investigated for this character, but these show much smaller

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BMNH 1964.4.30.67−68, inner face. N. Gobiomorphus hubbsi (Stockell, 1959) , Recent , Orongorongo river, New Zealand , BMNH 1964.4.30.69−70, inner face. O, P. Gobiomorphus cotidianus McDowall, 1975 , 2 specimens, Recent , Hawkes Bay, New Zealand , collection W. Schwarzhans, donated by Gerry Closs, inner face (O 1, P), ventral view (O 2). Q, R. Gobiomorphus gobioides (Valenciennes, 1837) , 2 specimens, Recent , Kakanui estuary, New Zealand , collection W. Schwarzhans, donated by Don Jellyman, inner face (Q 1, R 1), ventral view (Q 2). S. Philypnodon grandiceps (Krefft, 1864) , Recent , New South Wales, collection W. Schwarzhans, donated by AMS, inner face (S 1), ventral view (S 2).

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secondary than primary cteni ( Fig. 10 ). Clearly, the specialization of cteni in Mataichthys differs from Eleotris .

The otoliths of Mataichthys resemble those of the Gobiomorphus – Philypnodon group (see above) with the median sulcus and the roughly trapezoidal outline. However, Gobiomorphus otoliths are more rounded in outline than Mataichthys otoliths, and with less pronounced anterior−ventral and posterior−ventral projections. Otoliths of Philypnodon are more similar in outline (see Fig. 11K–S).

Species of Mataichthys apparently grew to a large size, possibly up to 25 cm long, judging from otolith sizes that exceed the in situ otolith of the holotype of M. bictenatus and comparison with a similarly sized modern species of Gobiomorphus , G. gobioides . Philypnodon species do not attain such sizes.

Mataichthys may be considered a plesiomorphic genus related to Gobiomorphus and Philypnodon . The separation of the three epurals of the caudal skeleton (versus the 2 nd and 3 rd usually fused in extant species), the trapezoidal outline of the otolith (versus rectangular to rounded in extant species of Gobiomorphus ) and possibly the high number of ventral fin rays (I+7 versus I+5–6) are considered plesiomorphic characters. The low number of anal fin rays (I+6 or 7 versus I+8–10) and the presence of alternating primary and secondary peripheral cteni on the scales (versus only primary cteni), however, are regarded as autapomorphic features indicating that Mataichthys may be sister group to Gobiomorphus , but not within the lineage of extant species of that genus.

Stevens and Hicks (2009), in an analysis of mitochondrial DNA, concluded that the seven living species of Gobiomorphus in New Zealand are descendants of a single lineage that separated from the two temperate Australian species and the sister genus Philypnodon . They postulate that the origin of the New Zealand Gobiomorphus lineage resulted from a single dispersal event from Australia some 16 to 28 Myr ago and felt that this finding is corroborated by unidentified skeleton findings interpreted to belong to Gobiomorphus ( McDowall et al. 2006b) . While there is nothing in our findings in the Bannockburn Formation that would contradict Stevens and Hicks’ (2009) logic, the identification of Mataichthys shows that the history of freshwater eleotrids in the Miocene of New Zealand was more complex, and included lineages which are now extinct.

Stratigraphic and geographic range.—Bannockburn Formation, Manuherikia River and Vinegar Hill.

Figures

Fig. 9. Comparison of the caudal skeleton of Miocene Mataichthys bictenatus and Recent eleotrids based on x−rays (scaled to same size). A. Gobiomorphus gobioides (Valenciennes, 1837), NMNZ P.32815. B. Gobiomorphus australis (Krefft, 1864), ZMUC Jrn.374. C. Gobiomorphus cotidianus McDowall, 1975, NMNZ P.12719−B. D. Philypnodon grandiceps (Krefft, 1864), ZMUC Jrn.115. E. Mataichthys bictenatus Schwarzhans, Scofield, Tennyson, and T. Worthy gen. et sp. nov. (holotype, NMNZ S.52752, location 4, Mata Creek, Bannockburn Formation, early Miocene). F. Butis humeralis (Valenciennes, 1837), ZMUC Jrn.93. G. Ophiocara porocephala (Valenciennes, 1837), ZMUC Jrn.101. H. Ophieleotris aporos (Bleeker, 1854), ZMUC P.781801. I. Culius fuscus (Bloch and Schneider, 1801), ZMUC P.781283. Abbreviations: EP, epurals; H 1+2, fused hypurals 1 and 2; H 3+4+ U, fused urostylar complex and hypurals 3 and 4; H 5, hypural 5; PH, parhypural; PU 2, preural centre 2.

Fig. 10. Comparison of the body scale morphology of Miocene Mataichthys bictenatus with Recent eleotrids. A. Mataichthys bictenatus Schwarzhans, Scofield, Tennyson, and T. Worthy gen. et sp. nov. (holotype, NMNZ S.52752, location 4, Mata Creek, Bannockburn Formation, early Miocene). B. Close−up of Mataichthys bictenatus depicting few preserved alternating primary and secondary cteni. C–E. Schematic drawings of the insertion of cteni on body scales in Gobiomorphus gobioides (Valenciennes, 1837) (from McDowall et al. 2006b) (C), Eleotris sp. (from Roberts 1993) (D), and Mataichthys bictenatus (E).