Pedro Mayoral was present at the 1540 muster as a member of Guevara's company. His last name, Mayoral, may indicate his profession, namely, a head herdsman. An expedition of this size would certainly require such a person.
1540-1550:
1540, Feb: Muster in Flint & Flint, Documents, Document 12 [4 horses, chainmail jacket with its skirts, beaver, sallet, native arms, w/Guevara]
Other Info:
?AGI, Pasajeros, L.2, E.2132 [August 18, 1535, Pedro Márquez, son of Pedro Sánchez de Mayoral and Juana Martín, citizen of Orehuela, to New Spain]
?ARChV, PL Civiles, Pérez Alonso (F), Caja 1715,2 [1577, 1578; Pleito de Pedro de Mayoral, de Fuenmayor (La Rioja); Juan Monje, de Fuenmayor (La Rioja); Concejo, justicia y regimiento de Fuenmayor (La Rioja); Manrique de Lara, Duque de Nájera, de Fuenmayor (La Rioja) Sobre Acusación de Pedro de Mayoral, arrendador de las alcabalas de Fuenmayor contra Juan Monje, tabernero por el duque de Nájera, señor de la mitad de dicha villa, de no pagar las alcabalas del vino vendidas en su taberna]
Relatives?: Gerhard, North Frontier, 106 [The only other encomienda here--Los Altos de Jalisco--Xalostotlitlán, held by Rodrigo de Frías in 1570, by Casilda de Mayoral in 1592-1595]