Macroplata has a unique character in its pectoral girdle: a distinct notch on the posterior border of the coracoid. The number of rib facets varies along the cervical vertebral column (27 in total) there is only one in the anterior vertebrae but two in the posterior ones. There are 5 pectorals, 19 dorsals, 4 sacrals and 30 caudals.
White (1940) referred the species Plesiosaurus longirostris to Macroplata, and this species has been wrongly regarded as the holoype by some authors. M. tenuiceps is the only valid species of Macroplata (Ketchum and Smith, 2010). Benson et al. (2011) referred material pertaining to ‘M. longirostris’ to Hauffiosaurus under the new combination Hauffiosaurus longirostris.
Type material: BMNH R5488, an almost complete skeleton with the distal parts of the limbs missing.