Apple and Google extended their dominance in the US smartphone market as 2012 neared its close, industry tracker comScore said on Thursday. The share of smartphone service subscribers relying on Google\'s Android software inched up to 53.7 percent in the three months leading up to December, while Apple\'s portion grew to 35 percent from 34.3 percent, comScore reported. The most popular mobile phones were made by South Korean consumer electronics titan Samsung, whose handsets were used by 26.9 percent of US telecom service subscribers, according to comScore. Apple\'s coveted iPhones accounted for 18.5 percent of subscribers in the overall mobile phone market, up from 17.1 percent at the end of August. Figures showing that the California companies are tightening their grips on the smartphone market were released as London-based Canonical weighed in with a business-oriented smartphone platform. Canonical announced a smartphone interface version of its Ubuntu desktop computer operating system based on open-source Linux code. Ubuntu smartphones will be able to dock with keyboards and monitors to provide personal computer capabilities, according to Canonical. \"We expect Ubuntu to be popular in the enterprise market, enabling customers to provision a single secure device for all PC, thin client and phone functions,\" Canonical chief executive Jane Silber said in a release. \"We also see an opportunity in basic smartphones that are used for the phone, SMS, web and email.\" Dell, Lenovo, and Hewlett Packard are listed among computer makers who build Ubuntu into machines for the global market. Ubuntu runs on more than 20 million desktop computers, according to Canonical. Smartphones powered by Ubuntu are not expected to be available until late this year or early next year.