Tuesday, March 28, 2023

[PaleoIchthyology • 2023] Khoratamia phattharajani • A New Sinamiin Fish (Amiiformes: Amiidae: Sinamiidae) from the Early Cretaceous of Thailand: Implications on the Evolutionary History of the Amiid Lineage

Khoratamia phattharajani 
Deesri, Naksri, Jintasakul, Noda, Yukawa, El Hossny & Cavin, 2023

The Sinamiidae are a family of halecomorph fishes (Holostei) stratigraphically limited to the Lower Cretaceous and confined to East Asia. The first species of sinamiids were discovered in China, and then new occurrences were recorded in Thailand and Japan. The three recognized genera, Sinamia, Siamamia and Ikechaoamia, are notably characterized by an unpaired parietal. Here, we describe a new genus and species of sinamiid based on material from the Aptian Khok Kruat Formation of Ban Krok Duean Ha, Nakhon Ratchasima, Thailand. The new taxon known from preserved specimens in 3D is characterized by four pairs of extrascapular and tall cylindrical teeth with a conical enamel stalk topped by an arrowhead-shaped acrodine cap, among other characters. A phylogenetic analysis of the halecomorph fishes shows that the new taxon is the sister of the other Thai species, Siamamia naga, and that the two are grouped with two Chinese genera in a strongly supported clade, the Sinamiinae. This subfamily is here grouped with the Amiinae that contained the extant Amia. This new discovery is a clue that Southeast Asia may have been a center of diversification for this fish clade, and the phylogenetic analysis reveals that amiines may have originated somewhere in Asia during the Cretaceous before they spread throughout the northern hemisphere.

Keywords: Halecomorphi; Amiidae; Sinamiinae; phylogeny; paleobiogeography; Khorat Plateau; Early Cretaceous; Khoratamia phattharajani

 (A) The section of the sample collection and (B) stratigraphic section of the study area.

Khoratamia phattharajani gen. et sp. nov., holotype NRRU-F01020023, skull roof in dorsal view: (A) interpretative line drawing (A’) and ventral view (B) interpretative line drawing (B’).
Scales bars: 1 cm.

Khoratamia phattharajani gen. et sp. nov., holotype NRRU-F01020023, photograph of the skull in right lateral view:
(A) interpretative drawing (A’) and left lateral view (B) line drawing (B’).
Scales bar: 1 cm.

 Holotype of Khoratamia phattharajani gen. et sp. nov., NRRU-F01020023:
 (A) photograph of the complete specimen in right lateral view, an arrow indicating the origin of the dorsal fin; (B) left lateral view, a white arrow indicating the position of the pelvic fin. The black box indicates the area enlarged in (C) (close-up of the teeth from a maxilla).
Scales bars: 2 cm (A,B); 0.1 cm (C).

Systematic Paleontology
Order AMIIFORMES Hay, 1929

Superfamily AMIOIDEA Bonaparte, 1839  
Family AMIIDAE Bonaparte, 1839  
Subfamily SINAMIINAE Patterson, 1973  

Khoratamia gen. nov.
Etymology. Khoratamia is derived from “Khorat“, the local name of the city and province of Nakhon Ratchasima, northeastern Thailand, which also gives the name to the Khorat plateau, + Amia (Greek).

Khoratamia phattharajani gen. et sp. nov.

Holotype. NRRU-F01020023 (Figure 3, Figure 4, Figure 5 and Figure 6). Anterior half fish with the dermal bones preserved.

Diagnosis. Sinamiin fish characterized by the following combination of characters: crescent preopercular with a broad dorsal end; four pairs of extrascapulars with the six medial ones rectangular in shape and the lateralmost ones elongate and triangular in shape; unpaired parietal tapering anteriorly and narrowing at its posterior extremity; pyriform-shaped gular plate with a smooth undulate posterior margin; ventral postinfraorbital elongated and tapering posteriorly; small dorsal postinfraorbital; high cylindrical teeth with conical enamel stalk marked by fine ridges and with an arrowhead-shaped acrodin cap with cutting carinae; rhombic scales with serrated posterior margins; no peg and socket articulation of the scales with a keel on its internal surface at the center of the scales.

Type locality. Ban Krok Duean Ha, Tambon Suranaree, Amphoe Muang Nakhon Ratchasima, Nakhon Ratchasima Province, NE Thailand.

Type horizon. Khok Kruat Formation, Early Cretaceous, Aptian.

Etymology. Khoratamia phattharajani derives from Phatthara + Rajan the designation of Somdet Phra Phatthara Maharat [พระภัทรมหาราช], a title given to King Bhumibol Adulyadej, (Rama IX, 5 December 1927 – 13 October 2016) in recognition of his research dedication and support for breeding Nile tilapia (Oreochromis niloticus), which has provided a new career for over a million Thai agriculturalists and became a primary protein source for the Thai people. The discovery of a new sinamiin fish resulting from cooperation between Thailand and Japan commemorates the close collaboration between the two countries in fish research and aquaculture, with Emperor Akihito presenting 50 Nile tilapias to King Rama IX in 1965.
โคราชเอเมีย ภัทรราชัน [ภัทรมหาราช]

Skull reconstructions of a Khoratamia phattharajani gen. et sp. nov. showing the pattern of sensory canals in dorsal view (A) and lateral view (B).
Scale bar: 2 cm.

The discovery of Siamamia in the Sao Khua Formation at the Phu Phok site extended the geographical distribution of sinamiins much farther south than their previous distribution, mainly in China. Then, the discovery of isolated sinamiin remains in several localities in Sao Khua Formation, and in the younger Khok Kruat Formation, indicated that these fish formed an important component of the continental aquatic vertebrate assemblages during the Early Cretaceous in what is now Thailand. The discovery of articulated material of a new genus and a new species of sinamiin in the Khok Kruat Formation, in a sister position to Siamamia, is an indication that diversification of this lineage had occurred in Southeast Asia, regardless of diversification in China. Note that another sinamiin fish specimen from the Phu Phok site, figured in Cavin et al. [2019], may correspond to a third distinctive taxon, thus reinforcing this region as a potential location for diversification of the clade.
The phylogenetic relationships obtained here, indicating the existence of a possible lineage of freshwater amiids formed by amiins and sinamiins, suggest that the extant freshwater Amia lineage may have originated in Asia before dispersal to North America.

Uthumporn Deesri, Wilailuck Naksri, Pratueng Jintasakul, Yoshikazu Noda, Hirokazu Yukawa, Tamara El Hossny and Lionel Cavin. 2023. A New Sinamiin Fish (Actinopterygii) from the Early Cretaceous of Thailand: Implications on the Evolutionary History of the Amiid Lineage. Diversity. 15(4); 491. DOI: 10.3390/d15040491
(This article belongs to the Special Issue Women’s Special Issue Series: Diversity)