This specimen comes from Monte San Giorgio, Besano Formation (Anisian, Middle Triassic), Sasso Caldo site.
R. acutenodosa specimens are usually small in size (with a diameter smaller than 4 cm). It is important to note that this species shows a great intraspecific variability, regarding the elements of the sculpture. Three node spirals are usually present (umbilical, lateral and marginal nodes). Marginal nodes are usually bigger, long and sturdy, whereas umbilical nodes are rounded, very faint and usually connected with indistinct ribs, sometimes not recognizable. Lateral nodes are more rounded and smaller than marginal nodes, which may assume the shape of rounded spikes.
The specimen is housed at the Museo di Storia Naturale di Milano.
Reference: Bindellini, G., Balini, M., Teruzzi, G., and Dal Sasso C. (2019). Ammonoid and Daonella zonation of the Sasso Caldo quarry (Besano Formation, Middle Triassic). Strati 2019 Congress, ST2.4 Ammonoids in stratigraphy: Abstract book, p. 87.
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