Holoptychiidae dzimtas daivspurzivis (Porolepiformes) no Latvijas augšējā devona Ketleru svītas nogulumiem

Abstract

Visotina T. 2022. Holoptychiidae dzimtas daivspurzivis (Porolepiformes) no Latvijas augšējā devona Ketleru svītas nogulumiem. Bakalaura darbā ir pētītas Ketleru svītas, Pavāru un Varkaļu ridas nogulumiežos sastopamo porolepiformo daivspurzivju (dzimta Holoptychiidae) atliekas, raksturota to izplatība, daudzveidība, morfoloģiskās īpatnības un veikts salīdzinājums ar citur pasaulē atrastajām un literatūrā aprakstītajām zivīm. Lielākā uzmanība pievērsta Holoptychius ģints pārstāvjiem, kuru atliekām ir precizēta to taksonomisko piederība. Pētījumā izmantoti materiāli no trīs Ketleru svītas mugurkaulnieku atlieku atrodnēm. Lauka darbi veikti 2019. un 2021.gadā, kad darba autore piedalījās materiālu no atseguma Pavāri2 Cieceres krastā netālu no Paksītes ietekas vākšanā un preparēšanā. Papildus tika izmantots materiāls no atseguma Pavāri-1 gar Cieceri pretī Pavāru mājām un Ketleru atsegumiem gar Ventu. Noteikta visu Holoptychiidae dzimtas zivju skeleta elementu piederība, morfoloģijas analīzei atlasītas ģints Holoptychius atliekas, kuras līdz šim netika detalizēti pētītas, un veikta šo atlieku morfoloģiskā un morfometriskā analīze. Ņemot vēra morfometriskās analīzes rezultātus, ir secināts, ka Holoptychius ģints zivju kauli no Ketleru un Pavāru atsegumiem visticamāk pieder vienai sugai. Salīdzinot Ketleru svītā atrastās Holoptychius atliekas ar literatūrā aprakstītajām, kā arī balstoties uz morfometrisko analīzi, tās tika noteiktas kā piederīgas Holoptychius ex gr. nobisissimus, ņemot vērā vispārējo līdzību ar Holoptychius nobilissimus no Skotijas, kas atrasta tikai nedaudz senākos nogulumos. Tomēr nevar izslēgt, ka Holoptychius no Ketleru svītas pieder sugai Holoptychius jarviki no Kvebekas, Kanāda, bet skaidri un pēc daudzām pazīmēm atšķiras no Holoptychius bergmanni no Arktiskās Kanādas.

Visotina T. 2022. Sarcopterygian fishes (Porolepiformes, Holoptychiidae) from the deposits of the Late Devonian Ketleri Formation of Latvia. The remains of porolepiform sarcopterygian fishes (family Holoptychiidae) occurring in the sedimentary rocks of the Ketleri Formation, Pavari and Varkali members have been studied in the bachelor thesis. Their distribution, diversity, morphological features have been described and a comparison with fishes found elsewhere in the world and described in the literature has been made. The focus is on the genus Holoptychius, whose remains have been refined in terms of their taxonomic affiliation. The material from three localities of fossil vertebrate remains from the Ketleri Formation was used. The fieldwork was carried out in 2019 and 2021, when the author participated in the collection and preparation of materials from the outcrop Pavāri-2 on the bank of Ciecere River near the mouth of the Paksīte River. In addition, material from the outcrop Pavāri-1 along the Ciecere opposite the abandoned Pavāri farmhouse and the Ketleri outcrops along the Venta River were used. The skeletal elements of all fish belonging to the family Holoptychiidae were identified; the remains of the genus Holoptychius, which have not been studied in detail so far, were selected for morphological analysis, and morphological and morphometric analyses of these remains were carried out. Taking into account the results of the morphometric analysis, it is concluded that the fish bones of the genus Holoptychius from the Ketleri and Pavāri localities most probably belong to the same species. Comparison of the remains of Holoptychius found in the Ketleri Formation with those described in the literature, as well as morphometric analysis, identified them as belonging to Holoptychius ex gr. nobisissimus, given the general similarity to Holoptychius nobilissimusfrom Scotland, found only in slightly older sediments. However, it cannot be excluded that Holoptychius from the Ketleri Formation belongs to the species Holoptychius jarviki from Quebec, Canada, but it clearly and based on many features differs from Holoptychius bergmanni from Arctic Canada.