Zantwijk (1985) deny that this was necessarily the case. Van Zantwijk demonstrates that at least in some altepetl the family-based nature of the calpulli was replaced with a hierarchical structure based on wealth and prestige. Newcomers from other altepetl were allowed to settle down and become part of the calpulli. Michael Smith (2003) shows that in some Nahua cities, notably Otumba, each calpulli specialised in a trade and took almost the form of a trade guild. Calpullis of Tenochtitlan The wards of Tenochtitlan, the Aztec capital, were also known as calpulli. The exact number of calpullis within the city is not known but Van Zantwijk (1985) based his calculations on a wide array of ethnohistorical sources. Van Zantwijk reached a number of 20 calpullis, 7 of which represented the original founding groups of Tenochtitlan and the remaining 13 being composed by groups coming to the city at later points in its development. Van Zantwijk assumed that each calpulli was ritually connected to one of the twenty day names. Below is a list of the twenty calpullis of Tenochtitlan based on the data from Van Zantwijk (1985): Founding calpullis Tlacatecpan Tlacochcalco Huitznahuac Yopico Chalman Izquitlan Cihuatecpan New calpullis Chililico Coatlan Apanteuctlan Acatliacapan Tzonmolco Tezcacoac Tlamatzinco Molonco Itlillan Tecpantzinco Xochicalco Coatlxoxouhcan Cuauhquiahuac Atempan Notes References Aztec society