APPARATUS COMPOSITION AND STRUCTURE OF THE PENNSYLVANIAN CONODONT GENUS GONDOLELLA BASED ON ASSEMBLAGES FROM THE DESMOINESIAN OF NORTHEASTERN ILLINOIS, USA
Ph. Vonbitter et Gk. Merrill, APPARATUS COMPOSITION AND STRUCTURE OF THE PENNSYLVANIAN CONODONT GENUS GONDOLELLA BASED ON ASSEMBLAGES FROM THE DESMOINESIAN OF NORTHEASTERN ILLINOIS, USA, Journal of paleontology, 72(1), 1998, pp. 112-132
Gondolella pohli new species assemblages, from the Desmoinesian of Ill
inois, confirm that the initial apparatus reconstruction of the conodo
nt genus Gondolella was incomplete and support later reconstructions b
ased on discrete elements. Gondolella pohli is the first species of a
biostratigraphically important conodont genus to be based primarily on
assemblages and to be placed within a known phylogeny. The 43 assembl
ages confirm the presence of seven distinct element types in the Gondo
lella apparatus and permit the reconstruction of each of these to a gr
eater degree than previously possible. Because the assemblages are pro
bably all fecal, the apparatus of the closely related Neogondolella is
used to interpret the apparatus plan-the position and identity of the
15 elements-single pairs of Pa, Pb, M, Sb-1, and Sb-2 elements, two p
airs of Sc elements, and an unpaired bilaterally symmetrical Sa elemen
t in the Gondolella apparatus. Using the similarity of the latter to t
he apparatuses of the better known ozarkodinids, we infer a three-dime
nsional fanlike apparatus architecture for the prioniodinid Gondolella
. Gondolella is apparently restricted to the Pennsylvanian and probabl
y evolved in the Early Pennsylvanian from the Idioprioniodus-Embsaygna
thus lineage by loss of the Pa element posterior process and by remode
lling of the other apparatus elements. Some species in the Idioprionio
dus-Gondolella lineage are atypical among prioniodinids in having deve
loped a Pa element platform; the lineage is also noteworthy because bo
th ancestor and descendant inhabited low-energy, low pH environments d
uring the Pennsylvanian.