Several reports have mentioned Pennsylvanian age Holometabola. Four taxa from these reports are accepted (Fig.
Of the reports that provide reasonable evidence for the existence of Pennsylvanian Holometabola, all were assigned conservatively to either basal or basalmost segments of modern orders, or to stem groups subtending modern orders (Fig.
A crucial evaluation of those records earlier than the Permian is important to place the presence of the four accepted Pennsylvanian Holometabola in proper context.
The wings of these two taxa were considered to have synapomorphies of the Holometabola, although eventually these taxa were removed from the Holometabola for different reasons--Metropator because its affinities where shifted to a nonholometabolous group, and Fatjanoptera because of a change in date from Upper Carboniferous to Lower Permian based on subsequent stratigraphic correlations.
There are three issues resulting from the geochronologic extension of fossil Holometabola to the Pennsylvanian-Mississippian Subperiod boundary or even earlier.
Relevance of alternative cladistic relationships to the timing of Holometabola origins
There are alternative cladistic arrangements of major clades within the Holometabola, although almost all recent analyses recognize three major superclades (Fig.
berthei, perhaps functioning similar to the crotchets of Lepidoptera, is attributable to an expression pattern of the Distal-less gene that regulates early developmental expression of abdominal appendages throughout basal clades of Holometabola (Labandeira and Santiago-Blay, 2002), similar to abdominal structures found in extant scorpionfly and sawfly caterpillars.
McKenna and Farrell (2010) used DNA sequences from 9 nuclear genes (elongation factor-1[alpha] (EF-1[alpha]), alanyl-tRNA synthetase (AATS), CAD, 6-phosphogluconate dehydrogenase (PGD), sans fille (SNF), triosephosphate isomerase (TPI), RNA Pol II, 28S, and 18S) to reconstruct the phylogeny of Holometabola with a focus on determining the phylogenetic placement of Strepsiptera.
9-genes reinforce the phylogeny of Holometabola and yield alternate views on the phylogenetic placement of Strepsiptera.
1997 Holometabola 18S, 28S Farrell1998 Chrysomeloidea, 18S Curculionoidea Shull et al.