|
Their inclusions have
been assigned to general groups to obtain
data on presence and abundance in the
different outcrops and to estimate the work
volume necessary for studying minoritary
groups. The relative abundance of some
groups found in other amber localities
reflects the unique characteristics of the
Iberian Plate, resulting from the climatic
regime and insularity during the Albian. As
during the Jurassic and Cretaceous the
Iberian Plate was an island, several
arthropod groups show endemism, as occurs
today in insular areas such as Macaronesia.
Several groups of
arachnids, crustaceans, and insects have
been recognized. Arachnids include mites,
pseudoscorpions, and spiders. Mites are
composed by the families Ametroproctidae,
Archaeorchestidae, Cepheidae, Erythraeidae,
and Trombididae. Spiders are represented by
the families †Lagonomegopidae, Oonopidae,
and Araneidae. The latter record is
considered the oldest of the group (orb-web
weaving spiders); orb-web fragments have
also been found within the amber, some with
trapped insects. This fact points out that
one of the spider web types better adapted
to catch flying insects most likely appeared
at the same time than modern insect groups,
linked with the radiation of the angiosperms.
On the other hand, several crustaceans
belonging to Tanaidacea (Alavatanaidae) and
Isopoda have been found.
Seventeen orders of
Hexapoda have been recognized, all insects
except to the Collembola: Archaeognatha,
Blattaria, Isoptera, Orthoptera, Mantodea,
Dermaptera, Psocoptera, Thysanoptera,
Hemiptera, Raphidioptera, Neuroptera,
Coleop¬tera, Trichoptera, Lepidoptera,
Diptera, and Hymenoptera. The most abundant
group in Peñacerrada I amber is Diptera,
followed by Hymenoptera. On the contrary,
San Just and El Soplao ambers have the
inverse relationship, first hymenopterans
and then dipterans. The ensemble of biota
preserved in Spanish amber includes aerial,
litter, and arboreal fauna, all of them
associated with different microecosystems
in/on/around the ancient resin-producing
trees.
Up to date, several new arthropod
families have been erected based on Spanish
amber material:
- Acariformes, Oribatida: Archaeorchestidae,
-
Crustacea, Tanaidacea: Alavatanaidae,
-
Hexapoda, Psocoptera: Archaeatropidae,
-
Hymenoptera: Alavarommatidae, Radiophronidae,
and Spathiopterygidae
-
Diptera: Chimeromyiidae.
A total of 52 genera and
57 species of insects have been described
from Spanish amber so far. A lot of
specimens are waiting to be studied, and
orders of insects have to be yet started to
examine. Significant differences have been
detected between the arthropod assemblages
from the nine Spanish outcrops in which
bioinclusions have been detected, although
there are some similarities. The use of
synchrotron imaging has opened new
possibilities in the systematic and
phylogenetic studies of some groups.
|
