24 



Tribolodon 



o 



c 



Exoglossin Clade Q 



01 



a 



to 



Hemitremian Clade 



Fig.2: Phylogenetic hypothe- 

 sis among the Chub Clade. 

 The synapomorphies suppor- 

 ting the nodes are as follo- 

 wing. Node A: Scale with 

 apically directed lateral radii: 

 distal lateral ethmoid hooked 

 posteriorly: supraethmoid 

 narrow: supraorbital small 

 with irregular shape: neu- 

 rocranium depressed with 

 flattened parietal region and 

 reduced orbitosphenoid sep- 

 tum: orbitosphenoid with ex- 

 tended parasphenoid contact. 

 Node B: Postorbital cranium 

 not elongated: weakly develo- 

 ped posttemporal fossa (from 

 Coburn & Cavender 1992). 



versed from other clades, reversed at the next few nodes, or vary intragenerically. Thus 

 the phylogenetic relationships of these genera in the Chub clade (Chub clade excluding 

 Exoglossin clade and Tribolodon) need to be further evaluated. 



According to my results and those of Cavender & Coburn 1 1987). some North American 

 and Eurasian minnow genera do form a monophyletic group, i.e.. the Hemitremian clade. 

 in the Chub clade of Coburn & Cavender (1992). as the sistergroup of the Exoglossin 

 clade (Fig.2); whereas, the Hemitremian clade + Exoglossin clade (including Plarygobio. 

 Hybognaihus, Dionda. Campostoma. Macriiybopsis, Erimystax, Nocomis, Exoglossum. 

 Phenacobius) form the sistergroup of Tribolodon in the Chub clade (Fig.2). 

 The Hemitremian clade includes eight genera, i.e.. Phoxinus. Couesius, Semotilus, He- 

 mitremia, Margariscus, Rhynchocypris, Eupallasella, and Lagowskiella. All Hemitrernians 

 share one synapomorph\ : the anterior placement of the anterior pterygiophores of the anal 

 fin. In Hemitrernians. the anterior few anal pterygiophores are placed forward to the first 

 haemal spine, at least one anal pterygiophore is positioned anteriorly to the last rib (Fig.3B- 

 C). Having studied all genera of exoglossins. other North America minnow genera, and 

 some Eurasian minnow genera. I could not find this character from outside of the He- 

 mitremian clade. Therefore. I interpret this character as an autapomorphy to support the 

 monophyly of the clade. The anterior position of the anterior anal pterygiophores was first 

 described and interpreted by Cavender cS: Coburn | 1 987 J to support a monophyletic group 

 including Phoxinus, Margariscus, Semotilus, Hemitremia, and Couesius. Later. Coburn £ 

 Cavender (1992) considered this character an evidence to support a monophyletic group 

 including almost all the Chub clade (onh Tribolodon excluded): and they interpreted the 

 absence of this character in exoglossins as a reversal of the anterior placement of the anal 

 pterygiophore(s). 



