Table 1.

Synonyms for somite-related structures of amphioxus, anamniotes, and amniotes

Group	Structure
Amphioxus	Somitocoel 1		Myotome 4	External cell layer 1	Sclerotome 1	Sclerocoel 9	Lateral plate 10
	Myocoel2	No equivalent	Myomesothelium5	Lateral wall6	Sclerablatt3		Seitenplatt3
	Myocöl3		Muskelblatt3	Dermomyotome7
				Dermatome8
				Cutisblatt3
Anamniote	Somitocoel 11	Dermomyotome	Myotome 13	External cell layer 11,14	Sclerotome 18	No equivalent	Lateral plate 19
	Myocoel12		Primary myotome11	Dermomyotome15
				Dermatome16
				Dermoendothelium17
Amniote	Somitocoel 20	Dermomyotome 21	Myotome 21	Central dermomyotome 21	Sclerotome 21	No equivalent	Lateral plate 21
				Dermatome22

Terms used in the present paper are in italics. ¹Present paper (without precedent). ² [15,68]. ³ [14]. ⁴ [3]; later in development, the myotome is generally termed ‘trunk muscle’. ⁵ [15]. ⁶ [15,68]. ⁷ [3]. ⁸ [69]. ⁹ [15]; ([14], considered this space as a subdivision of the myocoel). ¹⁰ [30]. ¹¹ [70]. ¹² [3]. ¹³ [71]; [3] later in development, the myotome is generally termed ‘trunk muscle’. ¹⁴[3] use the term ‘external cell layer’ alternatively with ‘lateral wall cells’. ¹⁵ [5]. ¹⁶ [72]. ¹⁷ [73] (name indicating later development as scale pockets in the dermis). ¹⁸ [71]; ([3] a region of sclerotome-derived cells (collectively the syndetome) gives rise to the tenocytes (myoseptal cells) at myotendinous junctions [5,38]). ¹⁹ [74]. ²⁰We will consider all chordate somitocoels homologous, although [3] have questioned that homology. The loose cells (collectively the arthrotome) in the amniote somitocoel are evidently sclerotome-related and give rise to the articular surfaces on the amniote axial skeleton [3]. ²¹ [33] Later in development, the myotome is generally termed ‘trunk muscle’. ²² [75].