Cerro del Castillo, Trelew: Aquitanian - Burdigalian, Argentina

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
Reptilia
Moreno and Mercerat 1891
Simpson 1946
Simpson 1946
Simpson 1946
Simpson 1946
Moreno and Mercerat 1891
Simpson 1946
Moreno and Mercerat 1891
Simpson 1946
Simpson 1970 1 specimen
Reptilia - Spheniscidae
Simpson 1946
Simpson 1946
Simpson 1946
Mammalia - Cetacea
Lydekker 1894 1 specimen
Mammalia - Cetacea - Balaenidae
2 specimens
Mammalia - Cetacea - Balaenopteridae
MDLP 5-13
Mammalia - Cetacea
1 specimen
Gaetán et al. 2019 2 specimens
(1 measurement)
see common names

Geography
Country:Argentina State/province:Chubut
Coordinates: 43.3° South, 65.3° West (view map)
Paleocoordinates:42.9° South, 61.8° West (Wright 2013)
Basis of coordinate:estimated from map
Time
Period: Neogene Epoch: Miocene
Stage: Aquitanian - Burdigalian 10 m.y. bin: Cenozoic 5
Key time interval: Aquitanian - Burdigalian
Age range of interval: 23.04 - 15.98 m.y. ago
Age estimate: 19.8 to 18.2 Ma (other)
Stratigraphy
Formation:Gaiman
Stratigraphic resolution:formation
Stratigraphy comments: formacion patagonica marina; early Miocene date form Fordyce (2002); In the area of the type locality of M. parvus, the lower part of Gaiman Formation overlies the continental Sarmiento Formation, which contains a mammal fauna correlating with the Colhuehuapian South American Land Mammal Age [51,52]. The latter was dated to 19.8-20.9 Ma, based on 40Ar/39Ar dating [53], thus providing a maximum age of ca. 20 Ma (earliest Burdigalian) for the lower part of the Gaiman Formation in this area. Since virtually all vertebrate material recovered so far originated from the lowermost levels of the Gaiman Formation, close to its contact with the Sarmiento Formation (Cozzuol 2010, pers. comm.), the age of Morenocetus is here assumed to be early Burdigalian. (Fordyce & Marx, 2013)

Both MLP 5-11 and 5-11 were originally reported to have come from the Patagonian Marine Formation [40]. The latter corresponds to the partially correlated Monte León and Gaiman formations, exposed in Santa Cruz (e.g. Garn Bajo de San Juan) and the lower Chubut river valley near Trelew (e.g. at Bryn Gwyn/ Loma Blanca), respectively [42]. In the area around Trelew, the lower part of Gaiman Formation overlies the continental Sarmiento Formation, which contains a mammal fauna correlating with the Colhuehuapian South American Land Mammal Age [43, 45]. The latter has been 40Ar/39Ar dated to 20.9– 19.8 Ma [46], thus providing a maximum age of 19.8 Ma (earliest Burdigalian) for the lower part of the Gaiman Formation in this area. Since virtually all vertebrate material recovered so far originated from the lowermost levels of the Gaiman Formation, close to its contact with the Sarmiento Formation [Cozzuol 2010, pers. comm.], an early Burdigalian age (19.8–18.2 Ma) is here assumed for M. parvus. (Marx & Fordyce, 2015)
Lithology and environment
Primary lithology: argillaceous sandstone
Includes fossils?Y
Lithology description: a mixture of sand and clay, including a stratum of sand capped by volcanic sand
Environment:shallow subtidal indet.
Geology comments: The holotype of A. moreni was found in “a mixture of sand and clay, including a stratum of sand capped by volcanic sand.” ([39]:1). The original description further explained that ”an apparently contemporaneous bed in Santa Cruz, also containing cetacean bones, has yielded oysters of an extinct species (Ostrea patagonica), and one skull from Chubut has one of the same oysters attached” [39: 1-2]. MLP 5-14 was later discovered at the same locality, described as “Castillo, frente a Trelew, Chubut” [40: 369], and reported to have come from the Patagonian Marine Formation (“formación patagónica marina”, [40: 364]).

The Patagonian Marine Formation corresponds to the partially correlated Monte León and Gaiman formations, exposed in Santa Cruz (e.g. Garn Bajo de San Juan) and the lower Chubut river valley near Trelew (e.g. at Bryn Gwyn/ Loma Blanca), respectively [42]. The Gaiman Formation consists of layers of marine sandstones and mudstones, as well as tuffs and tuffaceous sandstones. In addition, the lower part also contains occasional thin layers of Ostrea and bones of marine vertebrates [43]. Thus, the portion of the Gaiman Formation exposed near Trelew provides a likely match for the unit that yielded A. moreni [39, 40, 44].
11
In the area around Trelew, the lower part of Gaiman Formation overlies the continental Sarmiento Formation, which contains a mammal fauna correlating with the Colhuehuapian South American Land Mammal Age [43, 45]. The latter has been 40Ar/39Ar dated to 20.9– 19.8 Ma [46], thus providing a maximum age of 19.8 Ma (earliest Burdigalian) for the lower part of the Gaiman Formation in this area. Since virtually all vertebrate material recovered so far originated from the lowermost levels of the Gaiman Formation, close to its contact with the Sarmiento Formation [Cozzuol 2010, pers. comm.], an early Burdigalian age (19.8–18.2 Ma) is here assumed for A. moreni. (Marx & Fordyce, 2015)

Shows a shallow, storm-dominated marine environment with significant sea level oscillations.
Taphonomy
Modes of preservation:body,original phosphate
Size of fossils:macrofossils
Collection methods and comments
Reason for describing collection:taxonomic analysis
Metadata
Database number:47303
Authorizer:M. Uhen Enterer:M. Uhen
Modifier:M. Uhen Research group:vertebrate
Created:2005-02-22 11:25:32 Last modified:2025-02-24 15:20:29
Access level:the public Released:2005-02-22 11:25:32
Creative Commons license:CC0
Reference information

Primary reference:
12654. A. Cabrera. 1926. Cetaceos fossiles del Museo de La Plata. Revista del Museo de La Plata 29:363-411 [M. Uhen/M. Uhen/M. Uhen]

Secondary references:

37374 M. R. Buono, M. T. Dozo, and M. A. Cozzuol. 2010. Balaenidae (Mammalia, Cetacea, Mysticeti) del Mioceno de Patagonia: antecedentes, nuevos registros y proyecciones. Ameghiniana 46(4 Sup.):66R [M. Uhen/M. Uhen]
61705 C. M. Gaetán, M. R. Buono, and L. C. Gaetano. 2019. Prosqualodon australis (Cetacea: Odontoceti) from the Early Miocene of Patagonia, Argentina: Redescription and phylogenetic analysis. Ameghiniana 56(1):1-27 [M. Uhen/B. Shipps/M. Uhen]
91089 C. M. Gaetán, M. R. Buono, Y. Tanaka, N. D. Farroni, and V. N. Milano. 2025. Echoes from the Miocene: tracing the anatomy and phylogeny of Prosqualodon australis (Cetacea: Odontoceti). Journal of Systematic Palaeontology 23(1):2455753 [M. Uhen/M. Uhen]
12338 R. Lydekker. 1894. Cetacean skulls from Patagonia. Anales del Museo de la Plata II:1-13 [M. Uhen/M. Uhen/M. Uhen]
55050 F. G. Marx and R. E. Fordyce. 2015. Baleen boom and bust: a synthesis of mysticete phylogeny, diversity and disparity. Royal Society Open Science 2:140434 [M. Uhen/M. Uhen]
29788 F. P. Moreno and A. Mercerat. 1891. Catálogo de los pájaros fósiles de la República Argentina conservados en el Museo de La Plata [Catalogue of the fossil birds from the Argentine Republic housed in the Museo de La Plata]. Anales del Museo de La Plata. Paleontología Argentina 1:7-71 [M. Uhen/M. Uhen/M. Carrano]
25128 G. G. Simpson. 1946. Fossil Penguins. Bulletin of the American Museum of Natural History 87(1):1-100 [M. Uhen/M. Uhen]
25175 G. G. Simpson. 1970. Miocene penguins from Victoria, Australia, and Chubut, Argentina. Memoirs of the National Museum of Victoria 31:17-24 [M. Uhen/M. Uhen]