Arkell.1956.Jurassic..

58o THE ANDES OF SOUTH AMERICA
Jurassic ammonites with European genera and other species is striking at
all stages. There was formerly thought to have been an important influx
of Indian ammonites into South America with the Callovian (Jaworski,
1923), but this has proved to be an illusion. Revision by Spath of the
Cutch Jurassic ammonites described by Waagen, on which previous
identifications with Indian species had been based, showed that in each
case the South American species had been misidentified. Of the six
species of Indian Macrocephalites and three species of Indian Perisphinctes
listed from South America by Stehn (1924), only one is not rejected or
queried by Spath in his revision (and that one, M. magnumbilicatum
Waagen, is not confirmed by Spath for South America). A few Indian
species from the Callovian upwards are to be expected in South America
(pre-Callovian ammonites do not occur in Cutch), for another point
brought out by the revision of the Cutch ammonites is their close affinity
with the European. On the other hand none of the distinctively Indo-
Madagascan genera are known from South America (e.g. Bouleiceras of
the Toarcian, Obtusicostites, Sindeites, etc. of the Callovian). Instead,
there are correspondences with Western Australia and Canada in the
Bajocian (Pseudotoitej;).
Many of the Andean, like the Mexican, Tithonian ammonites were
assigned to 'boreal' Russian genera such as Virgatites, Craspedites, Simbirskites
(Burckhardt, 1903, 1911; R. Douville, 1910), but this was contested
by Uhlig (1911), and most of the disputed forms have since been
provided with new generic names. (Good figures of most of these
ammonites will be found in Burckhardt, 1903; Krantz, 1926 (reduced to
§); and Krantz, 1928). Burckhardt, however, still maintained his views
to the end (1930, p. 110), and in particular renamed as Craspedites limitis
the form previously figured by him as Perisphinctes aff. erinus (d'Orb.)
(1903, p. 52). Even Spath as late as 1931 (Cutch, p. 527) assigned Perisphinctes
mendozanus Steiger (1914, nom. nov. for Burckhardt's 'scythicus',
1903, pi. vii, figs. 1-8) and P. argentinus Haupt (1907, pi. viii, fig. 1) to the
boreal genus Dorsoplanites, but five years later, after studying the genus,
he thought the resemblance 'probably entirely superficial' (Spath, 1936,
Med. om Grenland, 99, p. 72). Leanza (1945, 1947) still admits the
Russian genus Riasanites in Argentina.
For the sake of brevity, the whole Andean province is tabulated below
as a single series of outcrops. Detailed regional treatments will be found
in Gerth (1935) and for the individual countries in useful books by Steinmann
(1929) for Peru (available in German and Spanish editions), by
Briiggen (1950) for Chile, by Windhausen (1931) and Weaver (1931) for
Argentina, and by Feruglio (1949) for Patagonia. For cross-sections of the
Andes see Douglas (1914, 1920-1), Jenks (1948) and Gonzales (1950).
A superb map is available (Stose, 1950), but this does not show some of the
small but important outcrops of marine Jurassic (e.g. at Caracoles) as
distinct from the volcanic rocks.
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