Savory - Arachnida 1977

104 U. DE ARACHNIDIS
and Euarachnida disappeared. The Pycnogonida were excluded, and
Nomomeristica were divided into four sub-classes, Limulava for the
extinct Copura, :Merostomata for Limulus and Eurypterida, Pectinifera
for the scorpions, and Epectinata for eight other orders. In the Epectinata
were six new· divisions known as super-orders; one of these, Caulogastra,
included Pedipalpi, Araneae and Palpigradi: the others contained
but a single order each. The features of this classification were
the expulsion cf the Pycnogonida and the expression of the belief that
the three orders of the Caulogastra are more closely related to each
other than to any other Epectinata; and also that no two other orders of
Epectinata arc so closely related that they can share a super-order.
Both these systems placed the scorpions in a section or sub-class
Pectinifera, which distinguished them from and contrasted them with
all other living Arachnida. This opinion expresses the traditional view
that the scorpions are more primitive arachnids than any others, and
this, as has been seen, is scarcely true.
Neither Lankester nor Pocock had given much attention to the
tion of the extinct orders other than Eurypterida, and this subject was
for the time adequately considered by Stormer (1944). He named
the phylum Arachnomorpha and divided it into two sub-phyla, Trilobitomorpha
and Chelicerata. The latter contained two classes, :\1erostomata
for Eurypterida and Xiphosura, and Arachnida for 13 orders,
covering the 17 orders described in Part Ill of this book. No suggestion
was made for the further relations of these orders, the names of which
were simply recorded in a linear series.
This aspect of the classification was the outstanding feature of
Petrunkevitch's of palaeozoic Arachnida in 1949. As a result of
detailed examination of a very large number of fossil Arachnida, he
threw new light on the probable course of evolution and expressed his
conclusions by placing the orders in four sub-classes which he named
Latigastra, Caulogastra, Stethostomata and Soluta. At almost the
same time the encyclopaedic "Traite de Zoologie" edited by Grasse,
printed a straightforward list of 14 orders.
Petrunkevitch used his system, with minor changes in nomenclature,
in his contribution to the "Treatise on Invertebrate Palaeontology",
edited by R. C. Moore, and published in 1955. It was followed almost
at once by a new classification, put forward by \V. B. Dubinin in 1957.
This author was evidently in an iconoclastic mood and he suggested a
drastic revision. The terrestrial Chelicerata were divided into four
classes, containing 21 orders, clearly the outcome of an entirely fresh
approach. More recently another
was adopted by the
present author in 1971. The three efforts may be compared in tabular
form.
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