In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The second twin , a male , had some features of Potter ' s facies , hypoplastic lungs , absent kidneys and ureters , and talipes equinovarus .
### Output Text:
The second twin , a male , had some features of Potter ' s facies , hypoplastic lungs , absent kidneys and ureters , and talipes equinovarus . 