Abstract Detail

Paleobotanical Section

Huerta-Vergara , Alma Rosa [1], CEVALLOS-FERRIZ , SERGIO RS [2].

Leaves and seed cone from the Cretaceous of Sonora, Mexico, suggesting the presence of Pinus.

A couple of years ago some conifer leaf and cones impressions/compressions from the Cretaceous of Northern and Southern Mexico were associated based on morphological characters to Pinaceae. Detailed observation of a twig demonstrated to be partially permineralized, and associated, but not in organic connection, to the impression of a seed cone.  Both were collected in the Cabullona Group near the Town of Esqueda, in the State of Sonora, Mexico. According to palynological studies these sediments date from the Upper Campanian (72 ma). The first fossil consists of a bent long branch with numerous scattered needle-leaves and leaf scars along the main axis. A permineralized section of the branch render ca. 40 thin sections, In transverse section the leaves are triangular to rhomboidal in shape, have a thick cuticle, rectangular epidermal cells, one to two layers of hypodermis with rectangular cells containing dark contents, plicate mesophyll parenchyma, transfusion tissue cells of irregular outline, a single vascular bundle with a cap of fibers, and 6 to 8 medial resin canals. In longitudinal section and parallel to the leaf margin rows florin rings are observed. The adaxial corner of each leaf exhibits an angle of ca. 90°, suggesting 4 leaf fascicles. Apparently leaves do have sheath fascicles. Two rubber molds were extract from a seed cone to observe the specimen in positive view, which highlights the ovuliferous scales and dorsal umbos with helically arrangement. The leaf characteristics suggest that the first fossil is a member of the genus Pinus, Subgenus Strobus, while the seed cone has more affinity to subgenus Pinus. If these two fossils represent the same species they may correspond to a new species with a mosaic of characters that today are distributed in different taxa. However, it is necessary to demonstrate that both specimens belong to the same plant in order to suggest the presence of a single species, meanwhile they are presented as two distinct species.

1 - Facultad De Ciencias, UNAM, Biología, Calle 2 #34, Col. Del Maestro; Azcapotzalco, México, D.F., N/A, 02040, Mexico
2 - Instituto de Geología, Paleontología, Ciudad Universitaria, Circuito de la Investigación Científica, Ciudad Universityariua CU, Coyoacan, 04510, Mexico

Keywords:
Pinus
Cretaceous
Sonora
Leaves
seed cone.

Presentation Type: Oral Paper:Papers for Sections
Session: 8
Location: Whitewater/Grove
Date: Monday, July 28th, 2014
Time: 10:45 AM
Number: 8009
Abstract ID:511
Candidate for Awards:Isabel Cookson Award