Cross-methodological evidence confirms soft eggs in sauropodomorph dinosaurs

NORELL, MARK A.; WIEMANN, JASMINA; MENÉNDEZ, IRIS; FABBRI, MATTEO; YU, CONGYU; MARSICANO, CLAUDIA A.; MOORE-NALL, ANITA; VARRICCHIO, DAVID J.; POL, DIEGO; ZELENITSKY, DARLA K.

NATURE

NATURE PUBLISHING GROUP

Año: 2022 vol. 610 p. 11 - 14

0028-0836

Choi et al.1 dispute recent morphological, histological, and geochemical evidence for a soft-shelled egg in Mussaurus2, an Early Jurassic sauropodomorph, based on three main assertions: (1) The crystalline carbonate signal detected in Mussaurus eggshell may represent original calcitic biomineral, despite resembling the carbonate in the limestone sediment matrix; (2) biologically informative spectra indicating a N-, O-, S-heterocyclic composition of 3-D translucent carbonaceous residues, a signature replicated by Choi et al.3, might represent graphite instead, an opaque form of elemental carbon that is commonly found in metamorphic rocks4; (3) birefringence, which would be indicative of calcite in the multilayered carbonaceous eggshell, may24 be obscured in the thin section by abundant organic material. Choi et al.1 did not perform new25 analyses of Mussaurus eggshell material, but, based on these assertions, scored Mussaurus26 eggshell as hard. They re-run our ancestral state reconstruction, obtaining a 52% probability of27 hard-shelled eggs in the ancestral dinosaur in contrast to our phylogenetic inference of an28 ancestrally soft egg2.