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| Parastylephorus anatoides Ridolfi, Schrøder, Bahrami, Yazdi, Roa-Varón, Marramà & Carnevale, 2026 Artwork by Lucrezia Bonardo |
Abstract
Stylephoriformes are a morphologically bizarre lineage of deep-sea fishes, currently represented by a single extant species, Stylephorus chordatus, the so-called tube-eye fish. The phylogenetic relationships of the Stylephoriformes were extensively debated until recent genomic studies proposed a sister-group relationship with the Gadiformes. The tube-eye fish exhibits a suite of highly derived features, including extreme cranial kinesis, a pipette-like oral apparatus specialized for suction feeding, and an elongate, naked ribbon-like body lacking scales. The evolutionary origin of these unique traits is largely unknown, in part due to the complete absence of a fossil record. Here, we describe the first-known fossil of the order Stylephoriformes, from Bartonian (c. 40 Ma) sediments of the Pabdeh Formation, Iran. On the basis of several unique morphological features (edentulous premaxillae and dentary, moderately enlarged pterygoid elements, reduced opercle, elongate ribbon-like body comprising more than 63 vertebrae, eight pectoral-fin rays, absence of basipterygia, and the presence of a complete series of well-developed lateral-line scales) the specimen is assigned to a new genus and species: Parastylephorus anatoides. The fossil exhibits a body physiognomy, oral apparatus and cranial architecture remarkably similar to those of the extant tube-eye, with the most derived features already present and closely comparable in morphology. This suggests that the new fossil represents a good example of long-term morphological stasis among marine teleosts, documenting the persistence of a highly specialized body plan for more than 40 myr.
Keywords: Parastylephorus anatoides, Bartonian, Iran, Pabdeh Formation, Paracanthopterygii
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| Parastylephorus anatoides gen. et sp. nov., holotype, IUGM 100897, from the Eocene of Babaheydar (Iran). Scale bar represents 10 mm. |
SYSTEMATIC PALAEONTOLOGY
Order STYLEPHORIFORMES sensu Miya et al. 2007
Family STYLEPHORIDAE Swainson 1839
Genus Parastylephorus nov.
Derivation of name: The genus name is derived from the Greek prefix para- (παρά), meaning ‘near’, combined with Stylephorus, the name of the only currently recognized stylephoriform genus. The name reflects the shared morphological characteristics with Stylephorus.
Remarks: As discussed above, the Stylephoriformes are a lineage currently represented by a single extant species, Stylephorus chordatus, which possesses a number of highly derived anatomical features, including a strongly modified buccal apparatus, extremely reduced first two vertebral centra, and a continuous dorsal fin along the entire dorsal margin of the body. The body plan of Parastylephorus gen. nov. closely resembles that of Stylephorus, although it has a set of distinctive traits. These include the maxilla with a well-developed posterior process, the expanded metapterygoid and ectopterygoid, and the reduced size of the opercular bones. In addition, Parastylephorus gen. nov. possesses body squamation, consisting of thin and delicate lateral-line scales, which are completely absent in Stylephorus.
Parastylephorus anatoides sp. nov.
Derivation of name: The name is derived from the Latin word Anas, meaning ‘duck’, and the Greek suffix -oides (-οειδής) meaning ‘resembling’ or ‘having the form of’.
Holotype: IUGM 100897 a partially preserved specimen on a single plate
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Artistic reconstruction of Parastylephorus anatoides gen. et sp. nov. Note that the tubular eyes are based on the condition characteristic of the extant Stylephorus chordatus. Artwork by Lucrezia Bonardo. |
Lorenzo Ridolfi, Ane Elise Schrøder, Ali Bahrami, Mehdi Yazdi, Adela Roa-Varón, Giuseppe Marramà and Giorgio Carnevale. 2026. A New fossil from the Eocene of Iran provides new insights regarding the evolution of the morphologically bizarre tube-eye fish. Papers in Palaeontology. DOI: doi.org/10.1002/spp2.70114 [11 August 2026]
