Cerro Yeso 1 (Eocene to of Argentina)

Also known as CY1

Where: Río Negro, Argentina (41.4° S, 69.6° W: paleocoordinates 43.6° S, 60.6° W)

• coordinate stated in text

• small collection-level geographic resolution

When: Lower Member (Las Chacras Formation), Bartonian to Bartonian (41.3 - 33.9 Ma)

• The proposed stratigraphic correlations and geochronological dates of the Las Chacras Formation indicate that the stratigraphic interval bearing the Lower Las Chacras fauna is younger than the maximum age estimated for the lower basalt flow exposed at Cerro Yeso (44 Ma.) The strong similarity with the Mustersan assemblage from the Rosado Member at Gran Barranca South of Colhué Huapi Lake, with a well constrained age of 38.16 – 37.4 Ma. (Dunn et al., 2013), suggests that the Lower Las Chacras Formation and its fauna is more likely of late Bartonian or early Priabonian age. Fossils occurs 22 m from the base of the formation in the measured section

• bed-level stratigraphic resolution

Environment/lithology: "floodplain"; massive, volcaniclastic, gray, green mudstone

• Floodplain and pyroclastic flow deposits
• light greenish to yellowish gray, laminated or massive volcaniclastic mudstones, intercalated with fine tuffs. Rhizoliths and fragmentary leaves and stems were also recognized.

Size class: macrofossils

Collection methods: Collected by Rodolfo Casamiquela during 1940’s and 1950’s. Further collection by Kramarz et al. 2022 in October 2017 and April 2018

Primary reference: A. Kramarz, E. Bellosi, M. Bond, A. M. Forasiepi, J. C. Fernicola, G. Aguirrezabala, and D. T. Rezende. 2022. Eocene mammals from volcaniclastic deposits of the Somun Cura Plateau: biostratigraphic implications for north Patagonia Paleogene. Andean Geology 49(2) [P. Mannion/G. Varnham/P. Mannion]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 225621: authorized by Philip Mannion, entered by Grace Varnham on 20.05.2022

Creative Commons license: CC BY (attribution)

Taxonomic list

 Astrapotheria - Trigonostylopidae
Trigonostylops sp. Ameghino 1897 placental
MJHG 101Pa, isolated upper molar (?CY1), specimen could not be found in the MJHG collection
 Astrapotheria - Astrapotheriidae
Astraponotus sp. Ameghino 1901 placental
MJHG 146Pa, right maxillary fragment with erupting P2 and alveolus for C1, partial symphysis with erupting incisor (i2?), roots of two incisors and partial alveoli for two incisors and canines, left mandibular fragment with erupting p3-p4, erupted m1-m2 and encrypted m3, and right mandibular fragment with erupting p4 and erupted m1-m2; MJHG 176Pa, probably associated i3 and partial upper molar; MACN Pv 17587, isolated left P3
 Theriamorpha - Pyrotheriidae
Propyrotherium saxeum Ameghino 1901 placental
MJHG 254Pa, isolated tusk
 Notoungulata - Archaeohyracidae
Pseudhyrax eutrachytheroides Ameghino 1901 notoungulate
MJHG-NCP 15, right maxillary fragment with M1?; MACN Pv 17217, associated right and left mandibular fragments with p2-m2
 Notoungulata -
Periphragnis sp. Roth 1899 notoungulate
MJHG 148Pa, associated left p3-m1, right p3, partial lower molar and partial upper molar
Periphragnis palmeri Roth 1904 notoungulate
MJHG-NCP 11, partial left mandibular ramus with p2-m3; MJHG-NCP 12, left maxillary fragment with M2-M3 and fragments of bones and teeth
 Notoungulata - Notohippidae
Puelia sigma Ameghino 1901 notoungulate
MACN Pv 17588, left mandibular fragment with m1-m2 (CY1); MACN Pv 17589, right mandibular fragment with p3-m3
 Cingulata - Dasypodidae
"Isutaetus depictus" = Pseudeutatus depictus
"Isutaetus depictus" = Pseudeutatus depictus Ameghino 1902 armadillo
MJHG-NCP 21, two isolated movable osteoderms; MJHG-NCP 22, one fixed isolated osteoderm