Dichondra argentea
Dichondra argentea, the silver ponysfoot or silver nickel vine, is a species of flowering plant in the family Convolvulaceae. It is disjunctly distributed in New Mexico, Texas, Mexico, Colombia, Bolivia, northwest Argentina, and southeast Brazil, and has gone extinct in Arizona. A creeping perennial reaching  high but growing  long, and hardy in USDA zones 10 through 12, in cultivation it is grown as annual, chiefly as a hanging accent plant or ground cover. There is a cultivar, 'Silver Falls'. References

Convolvulaceae
Flora of the South-Central United States
Flora of Mexico
Flora of Colombia
Flora of Bolivia
Flora of Northwest Argentina
Flora of Southeast Brazil
Plants described in 1806