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Gonkoken nanoi
Taxonomy
Gonkoken nanoi was named by Alarcón-Muñoz et al. (2023). Its type specimen is CPAP 3054, a limb element (R Ilium), and it is a 3D body fossil. Its type locality is Loma Koken, El Puesto, which is in a Maastrichtian coarse channel fill mudstone in the Dorotea Formation of Chile. It is the type species of Gonkoken.
Synonymy list
| Year | Name and author |
|---|---|
| 2023 | Gonkoken nanoi Alarcón-Muñoz et al. p. 3 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Gonkoken nanoi Alarcón-Muñoz et al. 2023
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| J. Alarcón-Muñoz et al. 2023 | Small-sized hadrosauroid dinosaur (total body length ~4 m) presenting the following autapomorphies: a scapula with an anteroventrally curved pseudoacromion process and an ilium with a medioventrally and anteroposteriorly well-developed sacral crest ex- tending posterior to the base of the postacetabular process. Gonkoken also differs from all other members of Hadrosauroidea in its unique combination of characters. Unlike the Hadrosauridae, it shows a maxilla with a jugal articular surface showing a prominent and caudally projecting dorsal tubercle; a dentary with a short diastema, mandibular symphysis oblique relative to its long axis, and tooth rows with less than 30 tooth positions that do not extend beyond the coronoid process and converge anteriorly with the lateral surface of the dentary; quadrate with a medial condyle that is not markedly elevated dorsally compared with the lateral condyle; a deltopectoral crest with a rounded laterodistal end extending less than 48% of the total length of the humerus; ilium with a nearly straight dorsal border and a supraacetabular process longer than 70% of the length of the iliac blade; and tibia with a cnemial crest extending less than 50% of the total length of the bone. In addition to these characters, Gonkoken differs specifically from South American Hadrosauridae by a scapula with a mediolaterally narrow coracoidal facet and a more ventrally curved pseudoacromion process, and an ilium with a more laterally curved preacetabular process, a less laterally developed supraacetabular process, and a shorter and ventrally oriented pubic peduncle. Gonkoken differs from early-diverging Hadrosauroidea in that it presents derived characters also found in Hadrosauridae: a premaxilla with a “double-layer” of denticles; a supraacetabular process anteriorly located with respect to the dorsal tuberculum of the ischial peduncle; the ratio between the base of the preacetabular process and the distance between the dorsal border of the ilium and the pubic peduncle is greater than 0.5; and a posteromedial condyle of the proximal end of the tibia that is more robust than the lateral one. Regarding non-hadrosaurids that are closely related to Hadrosauridae, Gonkoken differs from Eotrachodon in that the precircumnarial region of the premaxilla is more anteroposteriorly extended, lacking a caudally everted oral margin, and the maxilla has an articular surface for the jugal located anterior to the dorsal process, rather than posterior to it. Gonkoken differs from Lophorhothon in that the jugal process of the postorbital is pointing ventrally and the posterior edge of this process is slightly convex, rather than concave, and the ilium is higher, with a laterally less developed supraacetabular process, located anterior to the dorsal tubercle of the ischial peduncle. Gonkoken differs from Huehuecanauhtlus in that the preacetabular process of the ilium in dorsal view is markedly curved laterally, less curved ventrally, and its base is dorsoventrally narrower; the dorsal tubercle of the ischial peduncle of the ilium is less dorsally elevated; and the postacetabular process is approximately rectangular in lateral view, rather than triangular. |
Measurements
No measurements are available
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| Source: subo = suborder, o = order | |||||
| References: Marsh 1875, Kiessling 2004, Benton 1983 | |||||
Age range: Early/Lower Maastrichtian or 72.20000 to 66.00000 Ma
Collections: one only
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Early/Lower Maastrichtian | Chile (Última Esperanza) | Hadrosauridae indet. (type locality: 230991) |