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Link to original content: https://pubmed.ncbi.nlm.nih.gov/37327335
Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile - PubMed Skip to main page content
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. 2023 Jun 16;9(24):eadg2456.
doi: 10.1126/sciadv.adg2456. Epub 2023 Jun 16.

Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile

Jhonatan Alarcón-Muñoz  1   2   3 , Alexander O Vargas  1 , Hans P Püschel  1   4 , Sergio Soto-Acuña  1   2   5   6 , Leslie Manríquez  7 , Marcelo Leppe  8 , Jonatan Kaluza  9 , Verónica Milla  1   10 , Carolina S Gutstein  1   11 , José Palma-Liberona  12 , Wolfgang Stinnesbeck  13 , Eberhard Frey  14 , Juan Pablo Pino  1   2 , Dániel Bajor  1   2 , Elaine Núñez  1   2 , Héctor Ortiz  1   15 , David Rubilar-Rogers  3 , Penélope Cruzado-Caballero  16   17
Affiliations

Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile

Jhonatan Alarcón-Muñoz et al. Sci Adv. .

Abstract

In the dusk of the Mesozoic, advanced duck-billed dinosaurs (Hadrosauridae) were so successful that they likely outcompeted other herbivores, contributing to declines in dinosaur diversity. From Laurasia, hadrosaurids dispersed widely, colonizing Africa, South America, and, allegedly, Antarctica. Here, we present the first species of a duck-billed dinosaur from a subantarctic region, Gonkoken nanoi, of early Maastrichtian age in Magallanes, Chile. Unlike duckbills further north in Patagonia, Gonkoken descends from North American forms diverging shortly before the origin of Hadrosauridae. However, at the time, non-hadrosaurids in North America had become replaced by hadrosaurids. We propose that the ancestors of Gonkoken arrived earlier in South America and reached further south, into regions where hadrosaurids never arrived: All alleged subantarctic and Antarctic remains of hadrosaurids could belong to non-hadrosaurid duckbills like Gonkoken. Dinosaur faunas of the world underwent qualitatively different changes before the Cretaceous-Paleogene asteroid impact, which should be considered when discussing their possible vulnerability.

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Figures

Fig. 1.
Fig. 1.. Stratigraphic location of Gonkoken nanoi and geographic distribution of South American duck-billed dinosaurs.
(A) Stratigraphic section of the Dorotea Formation, indicating the location of the bones of Gonkoken nanoi. (B) Location of the duck-billed dinosaurs from South America: 1, Lapampasaurus cholinoi (Islas Malvinas locality, La Pampa Province, late Campanian to early Maastrichtian, Allen Formation); 2, Kelumapusaura machi (Matadero Hill, General Roca city, Río Negro Province, middle Campanian to early Maastrichtian, Allen Formation); 3, Bonapartesaurus rionegrensis (Salitral Moreno, General Roca Department, Río Negro Province, middle Campanian to early Maastrichtian, Allen Formation); 4, Huallasaurus australis (Arroyo Verde Puelén Department, Río Negro Province, late Campanian to early Maastrichtian, Los Alamitos Formation); 5, Secernosaurus koerneri (Río Chico, east of Lake Colhué Huapi, Chubut Province, Maastrichtian, Lago Colhué Huapi Formation); and 6, Gonkoken nanoi (Río de las Chinas Valley, Magallanes Region, late Campanian to early Maastrichtian, Dorotea Formation). (C) The quarry from which Gonkoken nanoi bones were excavated (bonebed level). (D) Detail of a nearly complete tibia.
Fig. 2.
Fig. 2.. Gonkoken nanoi gen. et. sp. nov., skeletal anatomy.
(A) Bones described in this work (white). Some elements are indicated specularly to facilitate their representation. (B) CPAP 5337, right premaxilla in lateral view. (C) CPAP 5341, incomplete left postorbital in lateral view. (D) CPAP 5340, incomplete right maxilla in lateral view. (E) CPAP 5370, left dentary in medial view. (F) CPAP 5343, right quadrate in lateral view. (G) CPAP 5344, cervical vertebra in anterior view. (H) CPAP 5346, dorsal vertebra in anterior view. (I) CPAP 5371, right scapula in lateral view. (J) CPAP 5352, left sternum in ventral view. (K) CPAP 5400, incomplete right rib in anterior view. (L) CPAP 5379, proximal portion of right radius in posterior view. (M) CPAP 5355, incomplete left ulna in anterolateral view. (N) CPAP 5353, left humerus in posterolateral view. (O) CPAP 3054 (holotype), right ilium in lateral view. (P) CPAP 5356, left postacetabular process in lateral view. (Q) CPAP 5357, proximal portion of right ischium in medial view. (R) CPAP 5363, proximal portion of left fibula in lateral view. (S) CPAP 5360, incomplete right femur in distal view. (T) CPAP 5358, left femur in anterior view. (U) CPAP 5362, left tibia in lateral view. (V and W) CPAP 5349, caudal vertebra in anterior and lateral views. (X) CPAP 5364, right metatarsal III in anterior view. Skeleton modified from (31). Scale bars, 50 mm [(B) to (G), (J), (K) to (N), (Q), (S), and (V) to (X)] and 100 mm [(H), (I), (O), (P), (R), (T), and (U)].
Fig. 3.
Fig. 3.. Gonkoken nanoi lacks several derived characters found in Hadrosauridae.
A selection of plesiomorphic characters is shown. (A and B) CPAP 5337, right premaxilla in dorsal (A) and lateral (B) views showing a circumnarial fossa without accessory fossa or foramina (1) and an anteroventrally deflected oral margin (2). (C) CPAP 5343, right quadrate in posterior view. The lateral condyle is not markedly offset ventrally with respect to the medial condyle, unlike Hadrosauridae (3). CPAP 5342, right dentary in medial (D) and dorsal (E) views, and CPAP 5370, left dentary in medial (F) and dorsal (G) views. Tooth rows do not exceed the coronoid process (4), the diastema is short (5), there are less than 30 dental positions (6), tooth row converges anteriorly with the lateral surface of the dentary (7), and the symphysis is oblique (8). CPAP 5353 (H), CPAP 5354 (I), and CPAP 5369 (J), left humeri in posterolateral view, in which the ratio between length of the deltopectoral crest and the total length of the humerus is lower than 0.48 (9), and the deltopectoral crest is mediolaterally short (10), with a widely arcuate laterodistal corner (11). (K and L) CPAP 3054, right ilium in lateral (K) and dorsal (L) views. The dorsal border of the ilium is almost straight (12), and the length of the supraacetabular process is higher than 70% of the length of the iliac blade (13). (M) CPAP 5362, left tibia in lateral view. In Gonkoken, the length of the cnemial crest is lower than the 50% of the total length of the bone (14). Scale bars, 50 mm (A) to (C) and 100 mm (D) to (M).
Fig. 4.
Fig. 4.. Derived characters of Gonkoken nanoi shared with Hadrosauridae.
G. nanoi supports these characters evolved before the origin of this family. (A) CPAP 5337, right premaxilla in ventral view, which shows a double-layer morphology (1). (B) CPAP 5340, right maxilla in lateral view, with a rostral maxillary foramen on the lateral surface of the bone (2). (C and D) CPAP 5344, mid-cervical vertebra in anterior (C) and lateral view (D). This cervical vertebra has elevated and well-developed postzygapophyseal processes, which are dorsally arched (3). (E) CPAP 5346, dorsal vertebra whose centrum has a “heart-shaped” articular surface (4). (F) CPAP 5347, mid-caudal vertebra with a hexagonal articular surface (5). (G) CPAP 5371, right scapula in medial view, which is dorsally arched (6). (H) CPAP 3054, right ilium in lateral view. The supraacetabular process is anteriorly located with respect to the dorsal tuberculum of the ischial peduncle (7). Furthermore, the ratio between the base of the preacetabular process (H1) and the distance between the dorsal border of the ilium and the pubic peduncle (H2) is greater than 0.5 (8). (I) CPAP 5360, distal end of the right femur in distal view, showing a deep intercondylar extensor groove, in which the condyles nearly meet anteriorly (9). In addition, the condyles are posteriorly well-developed (10). (J) CPAP 5362, left tibia in proximal view in which the posteromedial condyle is wider than the lateral condyle (11). Scale bars, 50 mm (A) and (F) and 100 mm [(B) to (E) and (G) to (J)].
Fig. 5.
Fig. 5.. Phylogenetic relationships.
Parsimony and Bayesian analyses recovered Gonkoken at a position transitional to Hadrosauridae, diverging shortly before the origin of this family; results of Parsimony are shown. The DIVA-like + j model (BioGeoBEARS) recovers Laramidia as the ancestral area for the most recent common ancestor of Eotrachodon and Hadrosauridae (node 1), as well as for the most recent common ancestor of Gonkoken and Hadrosauridae (node 2). Appalachia or Laramidia are recovered as ancestral areas for Hadrosauridae (node 3) and Laramidia as the ancestral area for Kritosaurini +Austrokritosauria (node 4). The names of the South American duck-billed dinosaurs are highlighted in red.
Fig. 6.
Fig. 6.. Biogeographic history of South American duck-bill dinosaurs.
Biogeographic statistics suggest that Gonkoken’s ancestors arrived from North America (in purple). The alternative hypothesis that Gonkoken’s ancestors could have dispersed from Europe into South America via Africa (Atlantogean hypothesis, in orange) was not supported by biogeographic statistics. Hadrosaurids related to the tribe Kritosaurini (in red) would also have dispersed from North America, giving rise to the clade Austrokritosauria in South America. These hadrosaurids may have never reached the same high latitudes as Gonkoken’s ancestors, possibly because they arrived later into South America. Paleogeographic drawing is based on information from the PALEOMAP project of C. Scotese and (10).
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