Telling the Evolutionary Time: Molecular Clocks and the Fossil Record

Figure 4.11

The known fossil record of modern bird gr

oups gives no indication that fossil finds can be expected in the Cretac

eous. Based o

n the distribution

in time of known fossils of three modern bird orders, the apod

iforms (swifts and hummingbirds), caprimulgiforms (goatsuckers),

and strigiforms (owls),

confidence intervals (95 per cent) are confined mainly to the Pala

eogene (early Tertiary), with just one barely creeping into t

he latest Cretaceous. The

‘megaclade’ consists of all three orders summed together. The levels of known finds

are indicated by horizontal bars (which may

represent one find or

many dozens of the same age). The more closely spaced the know

n finds, the shorter the confidence interval. Abbreviations: G, G

allic; S, Senonian; P,

Palaeocene; E, Eocene; O, Oligocene; M, Miocene; PI, Pliocene; Q

, Quaternary. Based on data in Bleiweiss (1998).

MICHAEL J.BENTON 73