Anomozamites sp.
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publication ID |
https://doi.org/ 10.26879/1293 |
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persistent identifier |
https://treatment.plazi.org/id/1B6F87DA-FFDE-FFC8-392D-BC8D53F4FC55 |
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treatment provided by |
Felipe |
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scientific name |
Anomozamites sp. |
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Figure 3 View FIGURE 3 A-B
Material examined. CFZ-Cr 3, Cr 4, Cr 7, Cr 27, Cr 53.
Description. Incomplete compound leaf, regularly segmented, with a length of 9.7– 8.9 cm and a width of 4.4 cm. Rachis traversed longitudinally by three distinct, about 0.2 cm wide, striae ( Figure 3A View FIGURE 3 ). Leaflets oppositely positioned, oblong and tapering towards the base, 2.5 cm long and 1.1 cm wide, length/width ratio is 2:1, laterally attached to the stem along their entire base, which is recurrent, apex rounded to obtuse ( Figure 3B View FIGURE 3 ). The macroscopic margin is straight (90˚), while the basiscopic margin is decurrent. Leaflet longitudinally traversed by six-11 distinct veins per leaflet that run perpendicular to the rachis, bifurcating once near the base ( Figure 3B View FIGURE 3 ).
Discussion. The fossil taxon Anomozamites comprises segmented leaves with leaflets as broad as long or twice as long as broad, with a broad base generally inserted laterally to the rachis, with numerous and parallel veins, simple or once-forked ( Figure 3A View FIGURE 3 ). In recent decades, the assignment of fossil leaves based on the classic definitions made by Harris (1932) for Anomozamites and Pterophyllum have been questioned ( Pott and McLoughlin, 2009), This has led to the revision and in many cases the taxonomic relocation of leaves. The macroscopic characteristics of the specimens from the Terreno Mixteco agree with the description amended by Pott and McLoughlin (2009) for Anomozamites , since they are leaves up to twice as long as they are wide. This is an essential character for their assignment, since according to Pott and McLoughlin (2009) the species of the genus Pterophyllum have leaves with leaflets that are more than twice as long as they are wide.
Other characters that corroborate the assignment to Anomozamites are the uniform shape of the leaflets along the length of the leaf, numerous strong parallel veins, simple or once bifurcated near the leaflet base. At the species level, the specimens were compared with A. angustifolium Pott et McLoughlin , specimens with affinity to the species A. triangularis and with A. sp. described by Lozano-Carmona et al. (2019) for the Zorrillo-Taberna Formation, since, although Person and Delevoryas (1982) mention for the first time the presence of the genus for the Rosario (Early Jurassic) and Zorrillo (Middle Jurassic) formations, the conservation status of the specimens did not allow assigning them to a species. On the other hand, the bibliographic review of the morphological characteristics of 30 species of Anomozamites described for Laurasia by Xu et al. (2019) and the characteristics described for the species from the Terreno Mixteco indicate that the specimens analyzed here differ from the species with which they were compared in the characteristics of the rachis and the size, shape, and number of veins per leaflet. It is therefore impossible to assign them to a previously described species of the genus.
Anomozamites is one of the most important genera of the extinct order Bennettitales and also one of the most diverse in Laurasia. Analysis of its distribution during the Mesozoic in Asia shows that Anomozamites appeared in China during the Late Triassic, where it reached its maximum diversity. At the end of this period, the number of its species decreased significantly but its distribution extended. It was in Mexico in the region of Tezoatlán (Oaxaca) during the Lower Jurassic and up to the Middle Jurassic, but finally disappeared from the planet during the Cretaceous ( Xu et al., 2019).
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