New or formerly poorly known, biochronologically and paleobiogeographically important gastroplitinid and cleoniceratinid (Ammonitida) taxa from middle Albian rocks of mid-western and Arctic Canada
Authors: Jeletzky J A 
Published: June 2014

The following new or poorly known, biochronologically and paleobiogeographically important ammonite taxa are described and figured from middle Albian rocks of the Canadian Western Interior Region and Sverdrup Basin: 1. Cleoniceratinae Whitehouse 1926 1a.
Cleoniceras (Cleoniceras) canadense sp. nov. 1b. Cleoniceras (Grycia) densicostata sp. nov. 1e. Cleogastroplites gen. nov. based on the unique species C. abberans sp. nov. 2. Gastroplitinae Wright 1952 2a. Pseudogastroplites gen. nov. with the following species: 2a I. P. articus sp. nov. (genotype);
and 2a II .!'._. nanus sp. nov. 2b. Anagastroplites gen. nov. based on the unique species A. tozeri sp. nov. 2c. Stotticeras gen. nov. based on the unique species S. crow??p. nov. 2d. Stelckiceras gen. nov. based on the unique species-St. liardense (Whiteaves 1889). 2e. Pseudopulchellia Imlay 1961
emend. with the following species: 2e I. Ps. pattoni Imlay 1961 (genotype); 2e II. Ps. balkwilli sp. nov.; 2e III. Ps. imlayi sp. nov.; and 2e IV. Ps. flexicostata (Imlay 1961). The following upward sequence of middle Albian (in the sense of Spath, 1926 non Casey 1961 nec. Owen 1971) cleoniceratinid
and gastroplitinid faunas is inferred to exist in the Upper shale member of the Christopher Formation, Sverdrup Basin: 1. Cleoniceras (Cleoniceras) canadense fauna corresponding approximately ta the lower part of Unnamed Zone F of the Canadian Western Interior Region and apparently to the
Lyelliceras lyelli Subzone of the European Standard. 2. Pseudopulchellia flexicostata fauna corresponding approximately to the upper part of Unnamed Zone F of the Canadian Western Interior Region as well as apparently to the upper part of the Hoplites dentatus Zone and the lower part of the
Euhoplites loricatus Zone combined. 3. Pseudogastroplites arcticus fauna corresponding approximately to the Pseudopulchellia pattoni Zone of the Canadian Western Interior Region and apparently ta the upper part of Euhoplites loricatus Zone of the European standard and 4. Anagastroplites tozeri fauna
corresponding approximately to the Stelckiceras liardense Zone of the Canadian Western Interior Region and apparently to the Dipoloceras cristatum Subzone of the European standard. These gastroplitinid faunas cannot be treated as regional paleontological zones as yet. However they are expected ta
become the basis of a new regional zonal standard valid for Canadian Arctic areas north of the Liard Plateau, northern and central Alaska and, possibly, the Pacifie slope of Siberia. The generalized Gastroplites sensu stricto Zone of the Canadian Western Interior Region is unknown in Sverdrup Basin.
It appears to be represented there by the unfossiliferous 200 m thick or thicker shale interval separating the Pseudogastroplites arcticus and Anagastroplites tozeri faunas. The Stotticeras crowanse faunule is known only from a solitary locality in the Liard River area which is believed to represent
the basal part of the Pseudopulchellia pattoni Zone. Stotticeras gen. nov. also occurs in central Alaska, where it appears to be associated with Pseudopulchellia flexicostata (Imlay). This genus is only questionably represented in the Sverdrup Basin. Stelckiceras gen. nov. appears to be restricted
to the Stelckiceras liardense Zone of the Canadian Western Interior Region which alone is believed to be correla­tive with the Dipoloceras cristatum Subzone of the European standard. Contrary ta the currently held ideas, it was not the Canadian Western Interior Basin but the Sverdrup Basin that
represented the evolutionary center of the sub­family Gastroplitinae in mid-Albian time. Most of mid-Albian gastroplitinid faunas of the Canadian Western Interior Basin (i.e. except its Gastroplites sensu stricto faunas) are not directly phylogenetically related. They represent, instead, a series of
separate episodes of migration of elements of principal gastroplitinid lineages which were endemic to and evolved uninterruptedly in the Sverdrup Basin. Each of these migration episodes ended in extinction. The situation changes early in late Albian, following an apparently complete draining of the
Sverdrup Basin, as the late Albian to early Cenomanian Neogastro­plites stock was evidently endemic to the Canadian and American areas of the mid­continental basin. Neogastroplites does not appear to be a descendant of Gastroplites sensu stricto or any other mid-Albian gastroplitinid stock of the
Canadian Western Interior Region, It seems to be, instead, a derivative of Pseudopulchellia ex gr. Ps. balkwilli sp. nov. native to Sverdrup Basin via Stelckiceras gen. nov. True representatives of Gastroplites sensu stricto and Neogastroplites are unknown anywhere outside of the mid-continental
basin of North America, except for the southern part of the Sverdrup Basin. All records of these genera in Alaska, on the Pacifie slope of Siberia, in the European Arctic, and in England are considered to be erroneous. All these gastroplitinids, such as Pseudogastroplites cantianus (Spath),
?Cleogastroplites subguadratus (Nagy) and other "Gastroplites" from Spitsbergen, Pseudopulchellia flexicostata (Imlay), "Gastroplites" spp. and "Paragastroplites" from northern and central Alaska, "Gastroplites" and "Neogastroplites" from the Pacifie slope of Siberia, belong to other genera native
to the Sverdrup Basin. So far as is known, the mid-Albian generation of the mid-continental basin of North America was only tenuously and possibly intermittently, connected with the Sverdrup Basin. In its turn, the mid-Albian Sverdrup Basin was a relatively small in­land sea which was only
tenuously, and possibly intermittently, connected with the contemporary basins of Alaska, northern Asia and European Arctic. This is evidenced by relatively to extremely rare occurrence of al gastroplitinid genera native to the Sverdrup Basin in these basins. This mid-Albian paleogeographic setup
appears to be incompatible with that reconstruction of Albian paleogeography of the Boreal Region based on the assumption of a globe of modern mean diameter and surface curvature (i.e. on the tenets of the orthodox plate tectonic hypothesis) as this reconstruction post­ulates the existence of an
improbably large Paleoarctic Ocean. Instead, this paleo­geographic setup agrees well with that reconstruction of Albian paleogeography of the Boreal Region based entirely on the concept of an expanding Earth as least from the early Mesozoic to the present day.