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| Isityumzi mlomomde
Gess & Clement, 2019
DOI: 10.7717/peerj.8073
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Abstract
New fossil lungfish remains comprising two parasphenoids, tooth plates and scales from the Famennian Witpoort Formation of South Africa are described. From the parasphenoid material, which bears similarity to Oervigia and Sagenodus but is nevertheless unique, a new genus, Isityumzi mlomomde gen. et sp. nov. is erected. Tooth plates and scales from the same locality may be conspecific but are not yet assigned until further material becomes available. The tooth plates closely resemble those of some taxa in the Carboniferous genus Ctenodus. The new taxon is significant as only the second Devonian lungfish described from the African continent, and for hailing from the high-latitude (polar) Waterloo Farm environment situated close to 70° south during the Famennian.
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| Palaeozoic Lungfish Parasphenoid Morphology. Isityumzi mlomomde n. gen. et sp., (A) partial parasphenoid (AM 4821); (B) and (C) part and counterpart of the holotype (AM 6501a/b); (D) interpretive drawing of the holotype. |
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| Figure 1: Palaeozoic Lungfish Parasphenoid Morphology. Isityumzi mlomomde n. gen. et sp., (A) partial parasphenoid (AM 4821); (B) and (C) part and counterpart of the holotype (AM 6501a/b); (D) interpretive drawing of the holotype. Comparative parasphenoid outlines: (E) Oervigia nordica (Lehman, 1959, Fig. 27), (F) Soederberghia groenlandica (Lehman, 1959, Fig. 17), (G) Rhinodipterus kimberleyensis (Clement, 2012, Fig. 3), (H) Rhinodipterus secans (Gross, 1956, Fig. 20), (I) Ctenodus cristatus (Sharp & Clack, 2013, Fig. 16), (J) Sagenodus i(Schultze & Chorn, 1997, Fig. 22), (K) Andreyevichthys epitomus (Krupina, 1987, Fig. 2), (L) Uranolophus (Denison, 1968, Fig. 8), (M) Chirodipterus australis (Miles, 1977, Fig. 76), (N) igogoensis (Miles, 1977, Fig. 77), (O) Griphognathus i(Miles, 1977, Fig. 75), (P) isp. (Berman, 1976, Fig. 4), and (Q) Eoctenodus microsoma (Long, 1987, Fig. 3). Parasphenoids not drawn to scale, redrawn from references given within. |
Systematic Palaeontology
OSTEICHTHYES Huxley, 1880
SARCOPTERYGII Romer, 1955
DIPNOMORPHA Ahlberg, 1991
DIPNOI Müller, 1844
Isityumzi mlomomde gen. et sp. nov.
Diagnosis. Lungfish with parasphenoid corpus and stalk equal in length, stalk narrow with parallel sides tapering to a single point. Corpus almost as wide as long and with a broad anterior angle of 90°.
Etymology/Derivation of name. Generic name ‘Isityumzi’, from isiXhosa language meaning a device for crushing (from ukutyumza, to crush). Specific name ‘mlomomde’ from isiXhosa meaning ‘long mouthed’.
Holotype. Complete parasphenoid, AM6501, Albany Museum, Grahamstown/Makhanda, Eastern Cape, South Africa.
Other material. AM 4821 (partial parasphenoid).
Horizon and type locality. Waterloo Farm, Grahamstown/Makhanda, South Africa; Witpoort Formation, Witteberg Group, Famennian, Late Devonian.
Note. The new taxon is erected from the parasphenoid material alone. Although we expect that the tooth plate and scale material are conspecific, we do not formally assign them to Isityumzi mlomomde gen. et sp. nov. here.
Conclusions:
• Isityumzi represents the only record of Late Devonian lungfish remains from western Gondwana (South America and Africa) and is described from its parasphenoid.
• The parasphenoid of Isityumzi bears similarity to Oervigia and Sagenodus but differs from those taxa in having a single pointed stalk (c.f. Oervigia) and the corpus and stalk being equal in length (c.f. Sagenodus).
• The lungfish tooth plates from the same horizon and locality are similar to the Carboniferous taxon Ctenodus cristatus.
• The new genus is the first Devonian lungfish described from a high-latitude environment, and the only lungfish known from the Witpoort Formation.
• It appears likely that Isityumzi conforms to a common morphotype for Famennian lungfishes in possessing a long head and tooth plates bearing radiating ridges.
• Isityumi adds further evidence for the co-occurrence of lungfish with tetrapod taxa.
Robert W. Gess and Alice M. Clement. 2019. A High Latitude Devonian Lungfish, from the Famennian of South Africa. PeerJ. 7:e8073. DOI: 10.7717/peerj.8073
