Page 10 - iCC044-201501_March
P. 10
We assembled a database of known fos- based on (i) the fossil records of Gond- PRODUCT
sil occurrences of cichlids on Gondwanan wanan landmasses currently inhabited by EFFICACY
landmasses based on the literature cichlids (South and Central America includ-
(see electronic supplementary material). ing the Caribbean, Africa, Madagascar, ALERT!
Different geological formations (or localities India, Arabia; cichlid fossils are known from
where there is no formalized lithostrati- all of these regions except Madagascar IMPORTANT
graphic framework) were assumed to and India), and (ii) these records combined NOTICE TO ALL
represent distinct sampling horizons. The with those of Australia and Antarctica,
function for the potential recovery of fos- former Gondwanan landmasses that lack eOWNERS OF
sil cichlids was estimated by tabulating cichlids but would be predicted to have
the number of sedimentary horizons (for- once been inhabited by the group under THE Cichlid
mations or localities) that meet three key the vicariance hypothesis. For both, we
criteria. First, candidate deposits must calculated CIs based on the record of all COLLECTION
be present on former Gondwanan land- cichlid fossils and estimated range exten-
masses. Second, candidate deposits must sions based on articulated cichlid remains Due to improvements
represent freshwater environments. Third, alone combined with appropriate recov- to the way we
candidate deposits must have the potential ery potential functions generated from the
to yield fossils of cichlids, were this group subset of deposits that yield complete fish publish, all previously
present. Sites yielding fish fossils (includ- specimens. This modified procedure is issued discs, and
ing but not restricted to cichlids)meet this more conservative and reflects the very real
final criterion. The nature of fossils (articu- possibility that the earliest cichlids might USB drives are now
lated or fragmentary) from sites satisfy- be recognized only on the basis of articu- obsolescent.
ing these conditions was also recorded. lated remains, as their isolated fragments
Because of uncertainty surround- might be too character-poor, too general- Which means that they will
ing age assessments, uniform recov- ized or both to permit reliable taxonomic continue to work, but it is no
ery potential was assumed within each attributions. longer possible to update the
epoch-level stratigraphic bin, with rela- collection by simply adding files
tive recovery potential given by the num- (b) Estimating time of evolutionary origin using the to the existing structure, and
ber of candidate horizons present in a distribution of ages of outgroups to cichlids that is not how it should be.
given interval divided by its duration.
Ambiguity surrounds the age of many Hedman [18] devised a Bayesian So, if you own the collection on
freshwater deposits. In this study, approach for constraining the time of ori- disc or USB you can acquire
imprecisely dated deposits are given their gin of a clade based on the distribution a completely up-to-date 8GB
oldest plausible age. This approach sys- of stratigraphic ages of successive out- USB drive for only $5 (which
tematically biases analysis towards older groups. This method requires that out-
age estimates for the time of clade origin, groups appear in the fossil record in an barely recovers the cost of the
thereby providing a more generous test order matching phylogeny and that they upgraded drive).
of the Gondwanan vicariance hypothesis. pre-date or are contemporary with the first
These data were used to generate point appearance of the focal clade. Such perfect If you can’t make it to a meeting, e-mail
estimates and 95% CIs for cichlid origin congruence is rare in empirical examples, webslave@cichlids.org.au and we’ll
and we adopt a proposed solution that arrange something for you.
conservatively excludes inconsistent ages.
facebook.cichlids.org.au
8
