Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Ontogeny, systematics, and evolution of the effaced Early Cambrian trilobites Peachella Walcott, 1910 and Eopeachella new genus (Olenelloidea)

Mark Webster
Ontogeny, systematics, and evolution of the effaced Early Cambrian trilobites Peachella Walcott, 1910 and Eopeachella new genus (Olenelloidea)
Journal of Paleontology (March 2009) 83 (2): 197-218

Abstract

Although used in biostratigraphy and in studies of early Cambrian trilobite evolution, the olenelloid genus Peachella has received little research attention. The ontogenetic and evolutionary origins of its derived features--an effaced cephalon and grossly inflated genal spines--have remained mysterious. Based on examination of new and existing collections, P. iddingsi and P. brevispina are here described in detail, including aspects of their respective ontogenies and the first description of the thorax of P. iddingsi. A new monotypic genus, Eopeachella, is also described from recently collected material from the Delamar Member of the Pioche Formation, Nevada. Eopeachella angustispina n. gen. n. sp., is less derived and stratigraphically older than both Peachella species and bridges the morphological gap between Peachella and typical olenelloids. The study reveals that cephalic effacement was progressively attained during both ontogeny and phylogeny in the Eopeachella+Peachella clade. Comparative ontogeny with other olenelloids reveals that progressive effacement was a trend superimposed upon and independent of a conserved pattern of ontogenetic shape change in the glabella and did not represent a peramorphic "extension" of glabellar ontogeny. Genal spine inflation was also achieved progressively (in a proximal-to-distal direction) through both ontogeny and phylogeny in the Eopeachella+Peachella clade. Genal spine inflation that convergently arose in later trilobite groups may have been similarly ontogenetically dynamic. Discovery of E. angustispina and P. brevispina in the Delamar Member raises olenelloid diversity in this member to at least 20 species; a higher diversity than in any coeval unit.


ISSN: 0022-3360
EISSN: 1937-2337
Coden: JPALAZ
Serial Title: Journal of Paleontology
Serial Volume: 83
Serial Issue: 2
Title: Ontogeny, systematics, and evolution of the effaced Early Cambrian trilobites Peachella Walcott, 1910 and Eopeachella new genus (Olenelloidea)
Author(s): Webster, Mark
Affiliation: University of Chicago, Department of the Geophysical Sciences, Chicago, IL, United States
Pages: 197-218
Published: 200903
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 69
Accession Number: 2009-032335
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
N36°52'60" - N38°40'00", W115°52'60" - W114°02'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200918
Close Modal

or Create an Account

Close Modal
Close Modal