Deficiency or absence of the sternocostal part is not uncommon.    From Wordnik.com.  [IV. Myology. The Muscles Connecting the Upper Extremity to the Anterior and Lateral Thoracic Walls] Reference

The sternocostal surface (Fig. 492) is directed forward, upward, and to the left.    From Wordnik.com.  [V. Angiology. 4b. The Heart] Reference

The Radiate sternocostal Ligaments (ligamenta sternocostalia radiata; chondrosternal or sternocostal ligaments).    From Wordnik.com.  [III. Syndesmology. 1F. Sternocostal Articulations] Reference

Its anterosuperior surface is rounded and convex, and forms the larger part of the sternocostal surface of the heart.    From Wordnik.com.  [V. Angiology. 4b. The Heart] Reference

Evidence for the existence of sternocostal movement in coelurosaurian theropods looks good, despite what Quick & Ruben (2009) say.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

It forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; it also forms the apex of the heart.    From Wordnik.com.  [V. Angiology. 4b. The Heart] Reference

The sternocostal articulation, however, allows the middle of the body of the rib to be drawn up, and in this way the transverse thoracic diameter is increased.    From Wordnik.com.  [III. Syndesmology. 5g. Articulation of the Manubrium and Body of the Sternum] Reference

It then follows the midsternal line to the lower end of the body of the sternum or on to the xiphoid process, where it turns lateralward and downward across the seventh sternocostal articulation.    From Wordnik.com.  [XII. Surface Anatomy and Surface Markings. 6. Surface Markings of the Thorax] Reference

In the position of expiration the lower border of the lung may be marked by a slightly curved line with its convexity downward, from the sixth sternocostal junction to the tenth thoracic spinous process.    From Wordnik.com.  [XII. Surface Anatomy and Surface Markings. 6. Surface Markings of the Thorax] Reference

The pyloric orifice is on the transpyloric line about 1 cm. to the right of the middle line, or alternately 5 cm. below the seventh right sternocostal articulation; it is at the level of the first lumbar vertebra.    From Wordnik.com.  [XII. Surface Anatomy and Surface Markings. 8. Surface Markings of the Abdomen] Reference

These articulations (I'd be interested to know if others have been described in the literature: this seems to be about it) indicate mobile, synovial sternocostal joints, exactly what Quick & Ruben (2009) say are absent.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

They are very thin, intimately blended with the radiate sternocostal ligaments, and strengthened at the upper and lower parts of the articulations by a few fibers, which connect the cartilages to the side of the sternum.    From Wordnik.com.  [III. Syndesmology. 1F. Sternocostal Articulations] Reference

The position of the various orifices is as follows: The pulmonary orifice is situated in the upper angle of the third left sternocostal articulation; the aortic orifice is a little below and medial to this, close to the articulation.    From Wordnik.com.  [XII. Surface Anatomy and Surface Markings. 6. Surface Markings of the Thorax] Reference

The line on the left side curves lateralward and downward across the fourth sternocostal articulation to reach the parasternal line at the fifth costal cartilage, and then turns medialward and downward to the sixth sternocostal articulation.    From Wordnik.com.  [XII. Surface Anatomy and Surface Markings. 6. Surface Markings of the Thorax] Reference

There are two in the articulation of the second costal cartilage and generally one in each of the other joints; but those of the sixth and seventh sternocostal joints are sometimes absent; where an interarticular ligament is present, there are two synovial cavities.    From Wordnik.com.  [III. Syndesmology. 1F. Sternocostal Articulations] Reference

The other three points are: (a) the seventh right sternocostal articulation; (b) a point on the upper border of the third right costal cartilage 1 cm. from the right lateral sternal line; (c) a point on the lower border of the second left costal cartilage 2.5 cm. from the left lateral sternal line.    From Wordnik.com.  [XII. Surface Anatomy and Surface Markings. 6. Surface Markings of the Thorax] Reference

—The more frequent variations are greater or less extent of attachment to the ribs and sternum, varying size of the abdominal part or its absence, greater or less extent of separation of sternocostal and clavicular parts, fusion of clavicular part with deltoid, decussation in front of the sternum.    From Wordnik.com.  [IV. Myology. The Muscles Connecting the Upper Extremity to the Anterior and Lateral Thoracic Walls] Reference

As discussed above, however, enormous sternal plates and 'special' sternocostal joints aren't required for avian-style air-sac ventilation in the first place, and saurischian dinosaurs (yes, sauropodomorphs as well as non-avian theropods) do possess the anatomical features required for an avian-style air-sac system.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

Quick & Ruben (2009) assert that sternal movement - of the sort used by birds - was not possible in non-avian dinosaurs; they say this because 'in nonavians, sternocostal articulations are flat wherein the distal sternal ribs abut the lateral edges of the sternum to form gliding, synovial joints or firmer, cartilaginous articulations and bird-like motion of the sternum is not permitted'.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

—The arch of the aorta begins at the level of the upper border of the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left side of the trachea and finally passes downward on the left side of the body of the fourth thoracic vertebra, at the lower border of which it becomes continuous with the descending aorta.    From Wordnik.com.  [VI. The Arteries. 2. The Aorta] Reference

(2009) paper is to assert that sternocostal movement didn't happen (when it probably did), and to propose that the thigh was somehow integral to the prevention of 'paradoxical collapse'.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference