John N. Vanarthos, chairman of Norris McLaughlin & Marcus/courtesy photo John N. Vanarthos, chairman of Norris McLaughlin & Marcus/courtesy photo

Norris McLaughlin & Marcus has elected John Vanarthos, a longtime partner who has served four years on the management committee, as the firm’s new chairman, and made changes at other leadership posts.

Vanarthos succeeds Matthew Sorrentino, who left the Bridgewater-based firm in April to become chief legal officer at Lehigh Valley Health Network, according to a release from the firm on Thursday.

The firm also said that David Blatteis and Graham Simmons have joined Dolores Laputka as co-chairs of the business law group, and Daniel Guadalupe and David Roberts joined Steven Hoffman as co-chairs of the litigation practice group.

Those additions came as Robert Gabrielski resigned as chairman of the business law group after 10 years, and Robert Mahony resigned as co-chairman of the litigation practice group after 12 years, the firm said.

All those in leadership roles are partners at the firm.

Vanarthos didn’t return a call seeking comment but, in a statement included in the release, he said: “I am honored that my colleagues have elected me to be chair of the firm. It is my goal to preserve the special culture we created at Norris McLaughlin over the last 65 years, while continuing to implement our strategic and growth plans for the future.”

Sorrentino took over as chairman in 2015, which was a milestone for the firm: He succeeded G. Robert Marcus, who had been chairman since 1974. Sorrentino, who came to Norris McLaughlin via its 2009 merger with Tallman, Hudders & Sorrentino of Allentown, also was notable for being a Pennsylvania-based leader of the firm.

At the time he took over as chairman, Sorrentino already had a relationship with Lehigh Valley Health Network, having served as its general counsel.

Vanarthos, a graduate of Rutgers University and Rutgers Law School-Newark, joined the firm in 1988 as an associate and made partner in 1996. He previously was chairman of the firm’s business law practice group, and most recently has been on the firm’s recruitment committee, the release said. He handles commercial transactions, mergers, acquisitions and corporate partnerships, and also advises tech companies on technology licensing information management and product development.

Blatteis is a member of the firm’s management committee and focuses on pharmaceutical, health care, and related practices.

Simmons is a business and real estate lawyer handling mergers and acquisitions and other transactions, often for clients in the financial services, health care, real estate, and automobile dealership industries.

Guadalupe represents clients in commercial litigation and as outside general counsel, handling business disputes, professional liability defense, arbitrations, trade secret and noncompete disputes, will and trust litigation, and international disputes.

Roberts handles complex commercial litigation involving partnership disputes, fraud, trade secrets, restrictive covenants, employment disputes, environmental matters, and insurance coverage.

Norris McLaughlin, apart from its Bridgewater home base, also has two offices each in New York and in Pennsylvania.

In the past decade-plus, Norris McLaughlin, previously based in Somerville, has expanded into new markets and at times been aggressive with acquisitions. In 2006, for example, it doubled the size of its New York office to 14 lawyers by merging with Szold & Brandwen, a real estate firm. A year earlier, it acquired five New Jersey attorneys from Schachter, Trombadore, Offen & Stanton in Somerville.

The firm grossed $59.7 million and had an average attorney head count of 115 in fiscal 2016, according to Law Journal data. Those figures were relatively flat year-over-year, as the firm had $60.3 million in gross revenue and an average attorney head count of 121 in fiscal 2015. Over a five-year period, the firm has grown gross revenue gradually, from $57.9 million in fiscal 2011, though it has done so with fewer lawyers, as the firm’s average attorney head count for that year was 143, historic data shows. The firm’s head count crested at about 150 at the time of the June 2009 merger.