Ardeidae Leach, 1820

Family Ardeidae Leach, 1820 View in CoL

The fossils are referred to the Ardeidae using characteristics of the tarsometatarsus and coracoid.

The tarsometatarsi (NMNZ S.50003 and S.51264) can be distinguished from other Aves by the combination of the following characters (based on Brodkorb, 1980 and pers. obs.):

1 Shaft long, narrow, wider than deep, narrowest just proximal of base of trochlea metatarsi II;

2 Hypotarsal ridges (crista hypotarsus) extends considerably less than ½ the length of the shaft;

3 Trochlea metatarsi II and III extend about the same distance distally;

4 Absence of a sulcus flexorius;

5 A distinct raised facet for the articulation of metatarsal I rather than a sulcus;

6 Trochlea metatarsi II–IV roughly in the same dorso-plantar plane;

7 No medial inflection in trochlea metatarsi II or lateral deflection in trochlea metatarsi IV.

In addition, herons are typified by a single small closed tendinal canal (canalis hypotarsi) and a single distinct hypotarsal ridge (crista hypotarsi), both not preserved in the available material.

The cranial extremity of the coracoid (NMNZ S.50004) can be diagnosed as an ardeid by the combination of the following characters (based on Brodkorb, 1980; Gilbert et al., 1981 and pers. obs.):

1 Brachial tuberosity (tuber. brachiale) present;

2 Raised oval humeral facet (facies artic. humeralis) faces dorsally;

3 Absence of a deep groove running along the medial face between the brachial tuberosity and the tip of the procoracoid (proc. procoracoideus);

4 Relatively small hook-shaped procoracoid bent slightly medially;

5 Distance between scapular facet (cotyla scapularis) and cranial most end of acrocoracoid (proc. acrocoracoideus) approximately equal to width of shaft at the procoracoid;

6 Scapular facet, raised and flattened but not cup-like.