Phylogenetic relationships of †Luisiella feruglioi (Bordas) and the recognition of a new clade of freshwater teleosts from the Jurassic of Gondwana

Abstract

Background: Teleosts constitute more than 99 % of living actinopterygian fishes and fossil teleosts have been studied for about two centuries. However, a general consensus on the definition of Teleostei and the relationships among the major teleostean clades has not been achieved. Our current ideas on the origin and early diversification of teleosts are mainly based on well-known Mesozoic marine taxa, whereas the taxonomy and phylogenetic relationships of many Jurassic continental teleosts are still poorly understood despite their importance to shed light on the early evolutionary history of this group. Here, we explore the phylogenetic relationships of the Late Jurassic (Oxfordian - Tithonian) freshwater †Luisiella feruglioi from Patagonia, in a comprehensive parsimony analysis after a thorough revision of characters from previous phylogenetic studies on Mesozoic teleosts.

Results: We retrieved †Luisiella feruglioi as the sister taxon of the Late Jurassic †Cavenderichthys talbragarensis, both taxa in turn forming a monophyletic group with the Early Cretaceous †Leptolepis koonwarri. This new so far exclusively Gondwanan freshwater teleost clade, named †Luisiellidae fam. nov. herein, is placed outside crown Teleostei, as a member of the stem-group immediately above the level of †Leptolepis coryphaenoides. In addition, we did not retrieve the Late Jurassic †Varasichthyidae as a member of †Crossognathiformes. The position of †Crossognathiformes within Teleocephala is confirmed whereas †Varasichthyidae is placed on the stem.

Conclusions: The general morphology of luisiellids is that of basal, stem Teleocephala; however, most of their synapomorphies have evolved independently in teleocephalans. Similarly, the resemblance between varasichthyids and crossognathiforms might be due to parallel evolution. In accordance to most teleostean phylogenies, our analysis shows that a major morphological change occurred along the stem line and are currently recorded at the level of †Leptolepis coryphaenoides. A stem-based total clade Teleostei has been accepted for this work.

Fig. 1

Different definitions of Teleostei represented on a simplified cladogram [4]. a. Total clade Teleostei sensu De Pinna [33]; b. Apomorphy-based clade Teleostei sensu Arratia [15]. Since the cladogram of Near et al. [4] includes only living taxa, †Dorsetichthys bechei, †Pachycormiformes, and †Aspidorhynchiformes have been added manually according to Patterson [9] and Arratia [15]

Fig. 2

Simplified strict consensus tree of 16 most parsimonious trees. Numbers given on branches: Bremer values in gray; Jackknife frequencies in red

Fig. 3

Traced history of characters 83 and 145. a. Character 83 – Composition of preopercular sensory canal: four or less, short simple tubules [0], seven or eight (up to 10), short simple or branched tubules [1], 12 or more long, simple or branched tubules [2]; b. Character 145 – Anterior extent of first uroneural: preural centra 4 or 3 [0], preural centrum 2 [1], preural centrum 1 [2], centra U1 or U2 [3]

Fig. 4

Traced history of characters 75 and 125. a. Character 75 – Characteristic notch (so-called leptolepid notch) in the anterodorsal ascending margin of the dentary: absent [0]; present [1]. b. Character 125 – Number of vertebrae (including preural centrum 1): fewer than 45 [0], between 45 and 65 [1], more than 65 [2]

Fig. 5

Alternative hypotheses for the relationships of †Luisiellidae fam. nov. a. Strict consensus forcing †Luisiellidae fam. nov. as sister group of Teleocephala. b. Strict consensus forcing the inclusion of †Luisiellidae fam. nov. within Teleocephala, as sister group of Osteoglossomorpha + Clupeocephala

Fig. 6

Distribution of marine and freshwater taxa on the stem Teleocephala

Fig. 7

Reduced consensus tree. Osteoglossomorphs have been deleted as well as other unstable taxa including the Jurassic †Varasichthys, †Bavarichthys and †Chongichthys, and the Cretaceous †Rhacolepis

Fig. 8

Stability of the node of †Leptolepis coryphaenoides and all teleosts more closely related to this taxon than to †Eurycormus. a. Phylogenetic hypothesis of Patterson [9] and Patterson and Rosen [10]; b. Phylogenetic hypothesis of Arratia [13]; c. Phylogenetic hypothesis of Arratia [14]; d. Phylogenetic hypothesis of Arratia [6, 15]