Friday, March 3, 2023

[PaleoIchthyology • 2023] Hyneria udlezinye • A high Latitude Gondwanan Species of the Late Devonian tristichopterid Hyneria (Osteichthyes: Sarcopterygii) from South Africa

 Hyneria udlezinye
Gess & Ahlberg, 2023

Painting by Maggie Newman

We describe the largest bony fish in the Late Devonian (late Famennian) fossil assemblage from Waterloo Farm near Makhanda/Grahamstown, South Africa. It is a giant member of the extinct clade Tristichopteridae (Sarcopterygii: Tetrapodomorpha) and most closely resembles Hyneria lindae from the late Famennian Catskill Formation of Pennsylvania, USA. Notwithstanding the overall similarity, it can be distinguished from H. lindae on a number of morphological points and is accordingly described as a new species, Hyneria udlezinye sp. nov. The preserved material comprises most of the dermal skull, lower jaw, gill cover and shoulder girdle. The cranial endoskeleton appears to have been unossified and is not preserved, apart from a fragment of the hyoid arch adhering to a subopercular, but the postcranial endoskeleton is represented by an ulnare, some semi-articulated neural spines, and the basal plate of a median fin. The discovery of H. udlezinye shows that Hyneria is a cosmopolitan genus extending into the high latitudes of Gondwana, not a Euramerican endemic. It supports the contention that the derived clade of giant tristichopterids, which alongside Hyneria includes such genera as Eusthenodon, Edenopteron and Mandageria, originated in Gondwana.

Systematic palaeontology


Diagnosis— Tetrapodomorph sarcopterygians with postspiracular bone present, vomers with long caudal process clasping the parasphenoid, circular scales with a median boss, and an elongate body with a trifurcate or rhombic caudal fin (modified from [3]).

HYNERIA Thomson, 1968

Type species— Hyneria lindae Thomson, 1968; Hyner, Pennsylvania, USA.

AM6540b and AM6528a, the two main blocks of the holotype of Hyneria udlezinye.
Each block also has a counterpart (not illustrated). A, AM6540b. Unlabelled bones all belong to a single large individual of the arthrodire placoderm Groenlandaspis riniensis [Long, et al. 1997]. B, AM6528a. This block also carries a jugal of the tetrapod Umzantsia amazana [Gess & Ahlberg, 2018] and a paranuchal of a small individual of Groenlandaspis riniensis.

Skull reconstruction of Hyneria udlezinye.
Dorsal (A) and lateral (B) views, drawn from photographs of a three-dimensional model, scaled to the size of the holotype.
Abbreviations: An, anocleithrum; Ang, angular; Cl, clavicle; Cle, cleithrum; De, dentary; It, intertemporal; Ju, jugal; La, lacrimal; M.Pr, median postrostral; Mx, maxilla; Op, opercular; Pa, parietal; Pi, pineal; Po, postorbital; Pop, preopercular; Pospl, postsplenial; Pp-St-Ta, postparietal, supratemporal and tabular (sutures not visible); Qj, qudratojugal; Sop, subopercular; Sq, squamosal; Sur, surangular.

Hyneria udlezinye sp. nov.  
"Probable eusthenopterid" [Gess & Hiller, 1995]
"Close to Eusthenodon" [Anderson, et al., 1999]
"Similar to Hyneria" [Gess & Coates, 2008]
"cf Hyneria" [Gess, 2011]
"Hyneria-like" [Gess & Whitfield, 2020]

Diagnosis—A very large tristichopterid, closely resembling Hyneria lindae but differing from it in the following respects: postparietal shield widening more strongly from anterior to posterior; lateral corner of tabular weakly developed; preopercular and lacrimal proportionally deeper; denticulated field on parasphenoid extends further anteriorly; subopercular more shallow; dentary fangs proportionately larger.

Etymology— an apposition, from isiXhosa ‘udlezinye’, meaning ‘one who eats others’, referring to the inferred predatory lifestyle of the species. IsiXhosa is the widely spoken indigenous language of south-eastern South Africa where the fossil locality is located.

Life reconstruction of the non-marine component of the Waterloo Farm biota. Hyneria udlezinye is shown together with the tetrapods Umzantsia amazana and Tutusius umlambo [Gess & Ahlberg, 2018], the placoderms Groenlandaspis riniensis and Bothriolepis africana [Long, et al., 1997], the coelacanth Serenichthys kowiensis [Gess & Coates, 2015], the lungfish Isityumzi mlomomde [Gess & Clemen, 2019], and a cyrtoctenid eurypterid.
Painting by Maggie Newman, copyright R. W. Gess.

The largest osteichthyan member of the Waterloo Farm vertebrate assemblage, a predatory sarcopterygian with a probable maximum length of nearly three metres, proves to be a new species of the genus Hyneria. This genus is otherwise only recorded from the late Famennian Catskill Formation of Pennsylvania. The new species, Hyneria udlezinye, differs from the type species Hyneria lindae in a number of minor but securely attested proportional characters relating to the skull roof, cheek, lower jaw and operculum. Hyneria now joins Eusthenodon and Langlieria as one of the derived, late, giant tristichopterids known from both Euramerica and Gondwana. The other confirmed members of this clade (MandageriaCabonnichthys and Edenopteron) are exclusively known from Gondwana. This strongly supports the contention that this clade represents a Gondwanan radiation [Olive, et al. 2020].

Hyneria udlezinye is the first tristichopterid to be recorded from a high palaeolatitude, all other members of the group coming from palaeoequatorial to mid-palaeolatitude localities. All previously recorded Gondwanan members of the derived tristichopterid clade come from Australia, leading Olive et al. [2020] to argue for an Australian origin for this clade. The new evidence from Waterloo Farm, however, suggests that a more general Gondwanan origin for this clade is highly likely. This once again demonstrates how inferences about biogeographical patterns have historically been skewed by a paucity of data from high-palaeolatitude localities. Such data can only come from Gondwana, as no continents extended into northern high latitudes during the Devonian. The Waterloo Farm lagerstätte provides a unique window into an almost unknown part of the Late Devonian world.

Robert W. Gess and Per E. Ahlberg. 2023. A high Latitude Gondwanan Species of the Late Devonian tristichopterid Hyneria (Osteichthyes: Sarcopterygii). PLoS ONE. 18(2): e0281333. DOI: 10.1371/journal.pone.0281333